WO2006130276A1 - System and method for hidden-refresh rate modification - Google Patents

System and method for hidden-refresh rate modification Download PDF

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Publication number
WO2006130276A1
WO2006130276A1 PCT/US2006/015710 US2006015710W WO2006130276A1 WO 2006130276 A1 WO2006130276 A1 WO 2006130276A1 US 2006015710 W US2006015710 W US 2006015710W WO 2006130276 A1 WO2006130276 A1 WO 2006130276A1
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WO
WIPO (PCT)
Prior art keywords
refresh
hidden
control signal
deasserted
memory device
Prior art date
Application number
PCT/US2006/015710
Other languages
French (fr)
Inventor
John Schreck
John R. Wilford
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Micron Technology, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Micron Technology, Inc. filed Critical Micron Technology, Inc.
Priority to EP06758601A priority Critical patent/EP1886316A1/en
Priority to JP2008514643A priority patent/JP2008542967A/en
Publication of WO2006130276A1 publication Critical patent/WO2006130276A1/en

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Classifications

    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
    • G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
    • G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
    • G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
    • G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
    • G11C11/402—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells with charge regeneration individual to each memory cell, i.e. internal refresh
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
    • G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
    • G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
    • G11C11/403—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells with charge regeneration common to a multiplicity of memory cells, i.e. external refresh
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
    • G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
    • G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
    • G11C11/406—Management or control of the refreshing or charge-regeneration cycles
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/34—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices
    • G11C11/40—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors
    • G11C11/401—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using semiconductor devices using transistors forming cells needing refreshing or charge regeneration, i.e. dynamic cells
    • G11C11/406—Management or control of the refreshing or charge-regeneration cycles
    • G11C11/40615—Internal triggering or timing of refresh, e.g. hidden refresh, self refresh, pseudo-SRAMs
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C2211/00—Indexing scheme relating to digital stores characterized by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C2211/401—Indexing scheme relating to cells needing refreshing or charge regeneration, i.e. dynamic cells
    • G11C2211/406—Refreshing of dynamic cells
    • G11C2211/4061—Calibration or ate or cycle tuning

Definitions

  • the present invention relates to electronic memories and, more particularly, to memory devices and methods performing hidden-refreshing of volatile memory elements.
  • DRAM dynamic random access memory
  • a DRAM refresh process is initiated by a processor or controller coupled to the memory device by supplying an appropriate control signal to a command or control interface of the memory device.
  • DRAMs hide some forms of refresh from the processor.
  • dynamic memory devices that require periodic refreshing of the memory cells
  • static memory devices that do not require refreshing of the memory cells have also become commonplace.
  • static random access memory (SRAM) devices require more transistors and circuitry to maintain the stored charge. Because of the additional circuitry and the increased area associated therewith, design tradeoffs are frequently undertaken to determine an appropriate form of memory for a system.
  • PSRAM pseudo static random access memory
  • a PSRAM device includes desirable characteristics of both DRAM devices and SRAM devices, namely, the low cost and large capacity of a DRAM device with the simplified interface and integration of an SRAM device.
  • the PSRAM device provides an improved memory cell density by employing higher density dynamic memory cells but also requires periodic refreshing in order to maintain the stored charge at levels sufficient to determine the logic state stored therein.
  • PSRAM devices incorporate refresh circuitry which is "hidden" within the memory device and thus relieves the system designer of the burden of programming a controller or processor to periodically execute the refresh process.
  • This hidden-refresh process within PSRAM devices must be periodically performed within the PSRAM device and requires the use of an appreciable amount of power delivered to the PSRAM device for executing the necessary refresh operation. Because power management is generally of great importance for systems that integrate memory devices, there is a need to provide an improved power conservation methodology for systems that integrate memory devices that utilize hidden-refresh techniques.
  • the present invention in exemplary embodiments, relates to a system and method for modifying a hidden-refresh rate for dynamic memory cells.
  • One embodiment of the present invention comprises a method for modifying a hidden-refresh rate of dynamic data in a memory device.
  • a control signal identifying a request from a processor is monitored at the memory device and a hidden-refresh of dynamic data within the memory device is performed at a first refresh rate when the control signal is asserted.
  • the dynamic data is refreshed at a second refresh rate when the control signal is deasserted for a predetermined duration.
  • a method for refreshing a memory device configured for hidden-refresh is provided.
  • the method includes generating a hidden-refresh clock signal and asserting a refresh pulse when a quantity of cycles of the refresh clock signal equals a count corresponding to a first refresh rate. Addresses corresponding to an array of dynamic memory cells are generated in response to the refresh pulse. The array of dynamic memory cells identified by the address are refreshed. The count corresponding to assertion of the refresh pulse is altered to a second refresh rate when the control signal received at the memory device is deasserted for a predetermined duration.
  • a hidden-refresh controller includes a hidden-refresh oscillator configured to generate a refresh clock and a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count.
  • the hidden-refresh controller further includes a hidden-refresh address counter configured to generate addresses corresponding to an array of dynamic memory cells in response to the refresh pulse.
  • a mode detector is configured to modify a first refresh rate of the array of dynamic memory cells to a second refresh rate when a control signal received at the mode detector is deasserted for a predetermined duration.
  • a memory device including an array of dynamic memory cells and a hidden-refresh controller.
  • the hidden- refresh controller couples to the array of dynamic memory cells during a hidden-refresh of the array of dynamic memory cells.
  • the hidden-refresh controller is further configured to monitor a control signal identifying a request from a processor at the memory device and refresh the dynamic data at a first refresh rate when the control signal is asserted.
  • the hidden-refresh controller is further configured to refresh the dynamic data at a second refresh rate when the control signal is deasserted for a predetermined duration.
  • an electronic system comprising an input device, an output device, a memory device, and processor device operably coupled to the input, output, and memory devices.
  • the memory device includes a memory array of dynamic memory cells and a hidden-refresh controller.
  • the hidden-refresh controller includes a hidden-refresh oscillator configured to generate a refresh clock and a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count.
  • the hidden- refresh controller further includes a hidden-refresh address counter configured to generate addresses corresponding to an array of dynamic memory cells in response to the refresh pulse.
  • a mode detector is configured to modify a first refresh rate of the array of dynamic memory cells to a second refresh rate when a control signal received at the mode detector is deasserted for a predetermined duration.
  • FIG. 1 is a functional block diagram of a system, including a processor and a memory device, that utilizes a hidden-refresh methodology, in accordance with an embodiment of the present invention
  • FIG. 2 is a flowchart of a mode detector for determining a functional state or mode of a memory device incorporating hidden-refresh techniques, in accordance with an embodiment of the present invention
  • FIG. 3 is a memory device mode detector configured according to the flowchart of FIG. 4 to set a hidden-refresh mode of a memory device, in accordance with an embodiment of the present invention
  • FIG. 5 is a memory device mode detector configured according to the flowchart of FIG. 6 to set a hidden-refresh mode of a memory device, in accordance with another embodiment of the present invention
  • FIG. 7 is a memory device mode detector configured according to the flowchart of FIG. 8 to set a hidden-refresh mode of a memory device, in accordance with a further embodiment of the present invention
  • FIG. 9 is a block diagram of an electronic system including a memory device configured with the hidden-refresh circuitry described herein, in accordance with yet another embodiment of the present invention.
  • FIG. 10 is a diagram of a semiconductor wafer including a memory device configured with the hidden-refresh circuitry described herein, in accordance with yet a further embodiment of the present invention.
  • FIG. 1 is a functional block diagram of a system 200 including a processor 202 coupled to a memory device 204.
  • the memory device 204 includes a hidden-refresh controller 206 for performing refresh operations and for adjusting the refresh rate according to a detected functional state of the memory device in relation to the processor 202.
  • the hidden-refresh controller 206 initiates a hidden-refresh operation upon the dynamic storage elements (e.g., dynamic memory cells) on aperiodic basis with the period being adjusted based upon the detected functional state of the memory device. Altering the hidden-refresh period or interval enables the memory device to consume less power when conditions are conducive to adequate data retention at a lengthened refresh period.
  • the present embodiments are described with reference to two memory device functional modes, namely an “active mode” and a “self-refresh mode,” the invention is not so limiting.
  • Those of ordinary skill in the art appreciate that various gradations of refresh rates or periods may be defined depending upon various factors including processor-to-memory device access frequencies, power levels, power transients, memory device fabrication process variations and techniques, as well as other conditions known and appreciated by those of ordinary skill in the art.
  • the memory device 204 in FIG. 1 may be configured as a pseudo static random access memory (PSRAM) device configured as a dynamic random access memory (DRAM) device utilizing a hidden-refresh methodology.
  • PSRAM pseudo static random access memory
  • DRAM dynamic random access memory
  • System 200 includes a processor 202 which applies addresses to an address decode logic 208 over an address bus ADDR.
  • the address decode logic 208 decodes a row address RA and a bank address BA which are applied to row address multiplexer 210 and bank control logic 212, respectively.
  • the row address multiplexer 210 applies either the row address RA received from the address decode logic 208 or a refresh row address RFRA received from the hidden-refresh controller 206 to a plurality of row address latch and decoder circuits 214A-D.
  • the bank control logic 212 activates the row address latch and decoder circuit 214A-D corresponding to either the received bank address BA or a refresh bank address RFBA from the hidden-refresh controller 206, and the activated row address latch and decoder circuit latches that decoded the received row address.
  • the activated row address latch and decoder 214A-D applies various control signals to a corresponding memory bank or array 216A-D to thereby activate a row of memory cells corresponding to the decoded row address.
  • the data in the memory cells in the accessed row is sensed and stored in sense amplifiers coupled to the memory bank or array 216A-D, which also refreshes the accessed memory cells as previously described.
  • the row address multiplexer 210 applies the refresh row address RFRA to the row address latch and decoders 214A-D and the bank control logic 212 uses the refresh bank address RFBA when the memory device 204 performs a hidden-refresh of the memory cells within memory bank or array 216A-D.
  • address decode logic 208 decodes row and bank addresses RA, BA, and a column address CA from the address received on address bus ADDR.
  • Address decode logic 208 may provide the column address CA to a column address counter and latch circuit 218 which, in turn, latches column address and applies the latch column address to a plurality of column decoders 220A-D.
  • the bank control logic 212 activates the column decoder 220A-D corresponding to the received bank address BA, and the activated column decoder decodes the column address CA from the counter and latch circuit 218.
  • the counter and latch circuit 218 may either directly apply the latched column address to the decoders 220 A-D, or may apply a sequence of column addresses to the decoders starting at the column address CA provided by the address decode logic 208.
  • the activated column decoder 220A-D applies decode and control signals to an I/O gating and data masking circuit 222 which, in turn, accesses memory cells corresponding to the decoded column address in the activated row of memory cells in the array 216A-D being accessed.
  • Data being read during a read operation from the activated memory bank or array 216A-D may be coupled through the I/O gating and data masking circuit 222 to a read latch 224.
  • the circuit 222 may supply N bits of data to the read latch 224, which may then apply two N/2 bit words to a multiplexer 226.
  • a data driver circuit 228 sequentially receives the N/2 bit words from the multiplexer 226 and also receives a data strobe signal DQS from a strobe signal generator 230 and a delayed clock signal CLKDEL from a delayed-lock loop (DLL) circuit 232.
  • the DQS signal has the same frequency as the CLK signal and is used by the processor 202 in latching data from the memory device 204 during read operations.
  • the data driver circuit 228 sequentially outputs the received N/2 bit words as corresponding data words DQ that, in a dual data rate (DDR) configuration, are synchronized with the rising and falling edges of the CLK signal, and also outputs the data strobe signal DQS having rising and falling edges in synchronism with the rising and falling edges of the CLK signal.
  • Each data word DQ and the data strobe signal DQS collectively define a data bus DATA coupled to the processor 202 which, during read operations, latches the each N/2 bit DQ word on the DATA bus responsive to the data strobe signal DQS.
  • the processor 202 during data write operations applies N/2 bit data words DQ, the strobe signal DQS on the data bus DATA.
  • the data receiver circuit 234 receives each DQ word and applies these to an input register 236 that is clocked by the DQS signal, hi a dual data rate (DDR) example and in response to the rising edge of the DQS signal, input register 236 latches a first N/2 bit DQ word and in response to a falling edge of the DQS signal, the input register latches the corresponding N/2 bit DQ word.
  • DDR dual data rate
  • Input register 236 provides the two latched N/2 bit DQ words as an N-bit word to a write FIFO and driver circuit 238, which clocks the applied DQ word into the write FIFO and driver circuit in response to the DQS signal.
  • the DQS word is clocked out of the write FIFO and driver circuit 238 in response to the CLK signal, and then is applied to the I/O gating and masking circuit 222.
  • the I/O gating and masking circuit 222 transfers the DQ word to the accessed memory cells in the active array 216A-D. While the present illustration is drawn to support a dual data rate, the various embodiments also contemplate lesser and greater data rates.
  • Control logic 240 receives a plurality of command and clocking signals from a processor 202 over a control bus CONT, and generates a plurality of control and timing signals to control the various memory device components 206-238 during operation of the memory device 204.
  • the command signals may include a chip enable signal CE*, a write enable signal WE*, an output enable signal OE*, a lower byte enable signal LB*, an upper byte enable signal UB*, a clock signal CLK, and may optionally include other control signals such as a sleep enable signal ZZ*.
  • One or more of the aforementioned signals may further include corresponding complementary signals, with the "*" designating a signal as being active when asserted low.
  • processor 202 drives the command signals CE*, WE* to values corresponding to a particular command such as a read or write operation.
  • the control logic circuit 240 latches and decodes an applied command and generates a sequence of control signals that control various components in the memory device to execute the function of the applied command.
  • the control logic circuit 240 latches command and address signals at positive edges of the CLK signal, while the input registers 236 and data driver circuits 228 may transfer data into and from the memory device 204 in response to either one or both edges of the data strobe signal DQS.
  • memory device 204 When data transfer occurs on both edges of the clock signals CLK, memory device 204 may be referred to as a double-data-rate (DDR) device with data being transferred to and from the device at double the rate of a conventional SRAM, which transfers data at a rate corresponding to the frequency of the applied clock signal.
  • DDR double-data-rate
  • PSRAM memory devices generally find application to low- power portable applications while providing high density memory storage.
  • Memory device 204 performs on-chip refresh operations, generally noted herein as a hidden-refresh of the dynamic memory cells within memory bank or memory array 216A-D.
  • the hidden-refresh process performed by hidden-refresh controller 206 requires no additional support from a system memory controller.
  • special attention is given to operational power consumption in the memory device during the hidden-refresh process.
  • the hidden-refresh controller 206 detects the need for refreshing the data stored within the memory banks or array 216A-D to prevent the loss of the data logic states due to leakage currents associated with dynamic memory elements.
  • the hidden-refresh controller 206 includes a hidden-refresh oscillator 242 configured to generate a hidden-refresh clock signal RFCLK.
  • the RFCLK signal provides a reference frequency for counting a quantity of clocks to determine a refresh interval or period.
  • Hidden-refresh controller 206 further includes a hidden-refresh refresh counter 244 coupled to the RFCLK signal of the hidden-refresh oscillator 242.
  • Hidden-refresh counter 244 counts a specific quantity of cycles of the RFCLK signal to determine when to assert a REFRESH PULSE signal.
  • a refresh period or rate is determined for maintaining the stored charge within the memory bank or array 216A-D.
  • Hidden- refresh controller 206 further includes a hidden-refresh address counter 246 configured to generate refresh addresses (e.g., refresh row addresses RFRA and refresh bank addresses RFBA) in response to a REFRESH PULSE.
  • refresh addresses e.g., refresh row addresses RFRA and refresh bank addresses RFBA
  • the refresh counter 244 is configurable by a mode detector 248 which determines if the memory device 204 is in one of at least two hidden-refresh modes, namely (i) an active mode wherein data is being or has recently been transferred between processor 202 and memory elements within the memory bank or array 216A-D or (ii) a self-refresh mode wherein an inactivity duration of the exchange of information between processor 202 and memory elements of the memory array has been detected.
  • the memory device 204 when actively exchanging data with the processor 202, defaults to an active mode of the hidden-refresh process.
  • the active mode of the hidden-refresh process provides for a more frequent execution of the refresh operation to mitigate data loss due to conditions such as voltage bumps or transients, moving inversions through the array, or long RAS low conditions that induce charge leakage in the dynamic memory cell.
  • the hidden-refresh counter 244 detects achievement of a COLfNT quantity of RFCLK signals corresponding to the current hidden-refresh mode (e.g., active mode or self-refresh mode) which causes the commencement of a hidden-refresh operation.
  • the hidden- refresh controller 206 applies control signals to the row address multiplexer 210 and the bank control logic 212 which cause the circuits to utilize the refresh row address RFRA and refresh bank address RFBA from the hidden-refresh controller 206 to sequentially access each row of memory cells in the memory array 216A-D and thereby refresh the memory cells.
  • the hidden-refresh controller 206 controls the refresh rate at which the memory cells in the arrays 216A-D are refreshed as a function of the determined memory device functional mode (e.g., active mode or self-refresh mode) as determined by mode detector 248 within hidden-refresh controller 206.
  • the determined memory device functional mode e.g., active mode or self-refresh mode
  • the hidden-refresh controller 206 includes a mode detector 243 which monitors one or more signals within memory device 204 to determine conditions that are conducive to the various functional modes. As stated, it is desirable to conserve power within system 200, therefore, when mode detector 243 determines conditions under which the hidden-refresh rate of the memory cells of memory array 216A-D may be reduced and still retain data integrity, mode detector 243 signals a change in the hidden-refresh mode from the higher or more frequent refresh rate "active mode" to the less frequent refresh rate of "self-refresh mode.” When the mode detector 243 determines a specific hidden- refresh mode, the mode detector 243 asserts a MODE signal to the hidden-refresh counter 244 to utilize a corresponding value of COUNT for determining when to assert the REFRESH PULSE signal.
  • the hidden-refresh controller 206 applies control signals causing the row address multiplexer 210 and the bank control logic 212 to utilize the refreshed row address RFRA and refresh bank addresses RFBA, respectively.
  • the hidden-refresh oscillator 242 may apply the refresh clock signal RFCLK to clock the hidden-refresh counter 246 which in turn sequentially generates the refresh row addresses RFRA and refresh bank addresses RFBA.
  • the sequentially generated refresh row addresses RFRA are applied through the multiplexer 210 and latched and decoded by the activated row address latch and decoder circuit 214A-D, with the bank control logic circuit 212 activating the circuit 214A-D corresponding to the refresh bank address RFBA.
  • the hidden-refresh controller 206 generates a given refresh bank address RFBA and then generates refresh row addresses RFRA to sequentially activate all rows in the memory array 216A-D corresponding to the bank address, and thereafter generates a new bank address and activates each row in the newly selected memory address, and so on for each memory array. In this manner, the refresh controller 206 sequentially activates rows of memory cells in the arrays 216A-D to thereby refresh the memory cells.
  • the refresh rate of the memory cells in the arrays 216A-D is determined by the rate at which the refresh counter 244 reaches the currently defined COUNT corresponding to the current functional refresh mode as conveyed to the hidden-refresh counter 244 by the MODE signal.
  • Mode detector 248 may be configured according to one or more of the embodiments of the present invention as illustrated with reference to FIGS. 3-8.
  • mode detector 243 functions according to the flowchart of FIG. 2.
  • the mode detector 243 (FIG. 1) monitors various signals to detect 302 specific conditions under which one refresh functional mode should be defined.
  • the mode is identified 304 as either an active mode where the refresh rate is performed more frequently 312, or a self-refresh mode where the refresh rate may be performed less frequently 308 in order to contribute to the conservation of power in system 200 (FIG. 1).
  • the conditions that define the various modes are continually monitored to determine when the modes may be changed to conserve power or when the modes should be changed in order to preserve data integrity.
  • FIG. 1 the mode detector 243 monitors various signals to detect 302 specific conditions under which one refresh functional mode should be defined.
  • the mode is identified 304 as either an active mode where the refresh rate is performed more frequently 312, or a self-refresh mode where the refresh rate may be performed less frequently 308 in order to contribute to
  • the hidden-refresh mode of either active or self-refresh is determined from analyzing a control signal, such as the chip enable CE* signal, to determine a state and duration associated therewith.
  • a control signal such as the chip enable CE* signal
  • the MODE signal will indicate the memory device 204 (FIG. 1) should be configured in a self-refresh mode designating conditions conducive for stretching or lengthening the hidden-refresh duration.
  • the mode detector 320 includes an element 322 that may be configured in various manners including a resettable delay element that propagates the CE* signal until it arrives at the output of the delay element.
  • element 322 may be configured as a resettable timer or counter that compares a count against a threshold or other value until the count equals the threshold and the MODE signal designates the determined hidden-refresh mode.
  • FIG. 4 is the corresponding flowchart for detecting the mode, in accordance with the present embodiment of the invention.
  • a hidden-refresh mode detector 320 (FIG. 3) evaluates 330 the current mode. If the current mode is active, then the state of chip enable CE* is determined 332.
  • chip enable CE* is asserted, this is an indication that ongoing accesses to the memory device 204 (FIG. 1) are being performed by the processor 202 (FIG. 1). Accordingly, power transients and other memory array access conditions demand a more frequent refresh of the memory cells and the MODE remains set to active and processing returns to evaluating the functional mode and any forthcoming inactivity in the memory device as indicated by an unasserted control signal, such as the chip enable CE* signal.
  • the mode is evaluated 330 and determined to be self-refresh, then the state of chip enable CE* is determined 334. If chip enable CE* remains unasserted, this is an indication of ongoing or sustained inactivity between the memory device 204 and the processor 202.
  • any power transients and other memory array access conditions are diminished and a less frequent refresh of the memory cells remains adequate for retention of the resident logic states resulting in the MODE remaining set to self-refresh with processing returning to an evaluation of the mode and any forthcoming activity in the memory device as indicated by, for example, an asserted chip enable CE* signal.
  • Determination 334 of an asserted chip enable CE* signal indicates that accesses to the memory device 204 have been resumed and are being performed by processor 202.
  • the MODE is set 336 to indicate an active mode and processing returns to evaluating 330 the mode and a determination 332 of any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
  • the element 322 (FIG. 3) is reset 338 through clearing of the delay line, resetting a duration timer/counter or other similar duration measuring element.
  • the achievement of a duration or threshold of the element 322 is measured 340. While the threshold is unachieved, the chip enable CE* signal is continuously monitored 342 and while the chip enable CE* signal remains unasserted, processing continues to return to measure 340 the timer/counter element 322 against the threshold. As stated, while measuring 340 for the achievement of the threshold, the chip enable CE* signal is monitored 342.
  • the MODE is set 344 to indicate the active mode and processing returns to evaluating 330 the mode and for determining 332 any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
  • the MODE is set 346 to indicate the self refresh mode and processing returns to evaluating 330 the mode and for determining 334 any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal. While the present embodiment has utilized the chip enable CE* signal as an indicator of activity and inactivity between the processor 202 (FIG. 1) and the memory device 204 (FIG. 1), other control or address signals maybe employed to indicate interaction or the lack thereof between the processor 202 and the memory device 204. Such modifications and adaptations are considered to be within the scope of the present embodiment of the invention.
  • FIG. 5 illustrates a logic block of a hidden-refresh mode detector functioning according to the flowchart of FIG. 6, in accordance with another embodiment of the present invention.
  • the functional refresh mode of either active mode or self-refresh mode is determined from analyzing the REFRESH PULSE signal to determine a pulse and consecutive occurrences of the pulse.
  • the refresh pulse counter 422 detects a series of consecutive occurrences of the REFRESH PULSE signal
  • the MODE signal will indicate the memory device 204 (FIG. 1) should be configured in a self-refresh mode designating conditions conducive for stretching or lengthening the hidden-refresh duration.
  • the mode detector 420 includes a refresh pulse counter 422 that may be configured in various manners including as a series of resettable latches that are clocked to propagate the chip enable CE* signal until the signal arrives at the output of the refresh pulse counter 422.
  • FIG. 6 is the corresponding flowchart for detecting the mode, in accordance with the present embodiment of the invention.
  • a hidden-refresh mode detector 420 (FIG. 5) evaluates 430 the current mode. If the current mode is active, then the state of chip enable CE* signal is determined 432. If chip enable CE* signal is asserted, this is an indication that ongoing accesses to the memory device 204 (FIG. 1) are being performed by the processor 202 (FIG. 1). Accordingly, power transients and other memory array access conditions may demand a more frequent refresh of the memory cells. Therefore, the MODE remains set to indicate the active mode and processing returns to evaluating the mode and any forthcoming inactivity in the memory device. Inactivity in the memory device may be indicated by an unasserted chip enable CE* signal resulting in a release of the latches of refresh pulse counter 422 (FIG. 5) from a reset state.
  • the state of the chip enable CE* signal is determined 434. If the chip enable CE* signal remains unasserted indicating ongoing inactivity between the memory device 204 and the processor 202, the affect of power transients and other memory array access conditions are diminished and a less frequent refresh of the memory cells may be adequate for retention of the resident logic states. Accordingly, the MODE remains set to indicate the self- refresh mode with processing returning to evaluate the mode and any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal. Determination 434 of an asserted chip enable CE* signal indicates that accesses to the memory device 204 have been resumed and are being performed by processor 202.
  • the MODE is set 436 to indicate an active mode and processing returns to evaluating 430 the mode and a determination 432 of any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
  • the refresh pulse counter 422 (FIG. 5) is released from reset 438 (i.e., the latches are released from being held reset and therefore inhibiting propagation of a signal).
  • the propagation of an unasserted chip enable CE* signal through the series of latches within refresh pulse counter 422 (FIG. 5) occurs unless the chip enable CE* signal becomes asserted and causes the suspension of propagation through the latches.
  • the chip enable CE* signal is monitored 440 and if the chip enable CE* signal becomes asserted, then the MODE remains in the active state and processing returns to evaluating 430 the mode and for determining 432 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal. If the chip enable CE* signal remains unasserted, then detection 442 of a first refresh pulse is performed. If the first refresh detection pulse is not detected, then processing returns to monitor 440 for assertion of the chip enable CE* signal causing the MODE to continue indicating the active mode and processing returns to evaluate 430 the mode and to determine 432 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal.
  • the MODE is set 448 to indicate the self-refresh mode and processing returns to evaluating 430 the mode and for determining 434 any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal.
  • FIG. 7 illustrates a logic block of a hidden-refresh mode detector functioning according to the flowchart of FIG. 8, in accordance with an embodiment of the present invention. Referring to both FIGS.
  • the functional refresh mode of either active mode or self-refresh mode is determined from analyzing a refresh complete signal, an example of which is a CARRY OUT signal from the hidden-refresh address counter 246 (FIG. 1) to determine consecutive occurrences of a completed refresh operation.
  • a refresh complete counter 522 detects a series of consecutive occurrences of the CARRY OUT signal
  • the MODE signal will indicate the memory device 204 (FIG. 1) should be configured in a self-refresh mode designating conditions conducive for stretching or lengthening the hidden-refresh duration.
  • the mode detector 520 includes a refresh complete counter 522 that may be configured in various manners including as a series of resettable latches that are clocked to propagate the chip enable CE* signal until the signal arrives at the output of the refresh complete counter 522.
  • FIG. 8 is the corresponding flowchart for detecting the mode, in accordance with the present embodiment of the invention.
  • a hidden-refresh mode detector 520 (FIG. 7) evaluates 530 the current mode. If the current mode is active, then the state of chip enable CE* signal is determined 532. If chip enable CE* signal is asserted, this is an indication that ongoing accesses to the memory device 204 (FIG. 1) are being performed by the processor 202 (FIG. 1). Accordingly, power transients and other memory array access conditions may demand a more frequent refresh of the memory cells. Therefore, the MODE remains set to indicate the active mode and processing returns to evaluating the mode and any forthcoming inactivity in the memory device.
  • Inactivity in the memory device may be indicated by an unasserted chip enable CE* signal resulting in a release of the latches of refresh complete counter 522 (FIG. 7) from a reset state.
  • the mode is evaluated 530 and determined to be self-refresh, then the state of the chip enable CE* signal is determined 534. If the chip enable CE* signal remains unasserted indicating ongoing inactivity between the memory device 204 and the processor 202, the affect of power transients and other memory array access conditions are diminished and a less frequent refresh of the memory cells maybe adequate for retention of the resident logic states. Accordingly, the MODE remains set to indicate the self- refresh mode with processing returning to evaluate the mode and any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal.
  • Determination 534 of an asserted chip enable CE* signal indicates that accesses to the memory device 204 have been resumed and are being performed by processor 202. Accordingly, power transients and other memory array access conditions likely require a more frequent refresh of the memory cells and, therefore, the MODE is set 536 to indicate an active mode and processing returns to evaluating 530 the mode and a determination 532 of any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
  • the refresh complete counter 522 (FIG. 7) is released from reset 538 (i.e., the latches are released from being held reset and therefore inhibiting propagation of a signal).
  • the propagation of an unasserted chip enable CE* signal through the series of latches within refresh complete counter 522 (FIG. 5) occurs unless the chip enable CE* signal becomes asserted and causes the suspension of propagation through the latches.
  • the chip enable CE* signal is monitored 540 and if the chip enable CE* signal becomes asserted, then the MODE remains in the active state and processing returns to evaluating 530 the mode and for determining 532 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal. If the chip enable CE* signal remains unasserted, then detection 542 of a first refresh complete, namely a CARRY OUT, signal is performed. If the first CARRY OUT signal is not detected, then processing returns to monitor 540 for assertion of the chip enable CE* signal causing the MODE to continue indicating the active mode and processing returns to evaluate 530 the mode and to determine 532 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal.
  • the MODE is set 548 to indicate the self-refresh mode and processing returns to evaluating 530 the mode and for determining 534 any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal.
  • the present embodiment has utilized the chip enable CE* signal as an indicator of activity/inactivity between the processor 202 (FIG. 1) and the memory device 204 (FIG. 1), other control or address signals maybe employed to indicate interaction or the lack thereof between the processor 202 and the memory device 204.
  • other control or address signals maybe employed to indicate interaction or the lack thereof between the processor 202 and the memory device 204.
  • Such modifications and adaptations are considered to be within the scope of the present embodiment of the invention.
  • FIG. 9 is a block diagram of an electronic system including a memory device configured in accordance with an embodiment of the present invention.
  • An electronic system 550 includes an input device 552, an output device 554, a processor 202, and a memory device 204 incorporating a hidden-refresh controller 206, as described above with reference to FIGS. 1-8.
  • the memory device 204 of FIGS. 1-8 may be fabricated on a semiconductor wafer 560.
  • semiconductor substrates other than a semiconductor wafer also fall within the scope of the present invention, including, for example, Silicon-On-Sapphire (SOS) substrates and Silicon-On- Glass (SOG) substrates.
  • SOS Silicon-On-Sapphire
  • SOG Silicon-On- Glass

Abstract

A system (200) and method for modifying a hidden-refresh rate for dynamic memory cells (21GD) includes monitoring a control signal (CE*) from a processor (202) and performing a hidden- refresh of the dynamic data at a first refresh rate when the control signal (CE*) is asserted. The dynamic data is refreshed at a second refresh rate when the control signal is deasserted for a predetermined duration. A hidden-refresh controller (206) couples to the array of dynamic memory cells (216D) during a hidden-refresh of the array of dynamic memory cells. The hidden- refresh controller (206) is further configured to monitor a control signal identifying a request from a processor at the memory device and refresh the dynamic data a first refresh rate when the control signal is asserted. The hidden-refresh controller (206) is further configured to refresh the dynamic data at a second refresh rate when the control signal (CE*) is deasserted for a predetermined duration.

Description

SYSTEM AND METHOD FOR HIDDEN-REFRESH RATE MODIFICATION
BACKGROUND
Field of the Invention: The present invention relates to electronic memories and, more particularly, to memory devices and methods performing hidden-refreshing of volatile memory elements.
State of the Art: Memory cells, and in particular dynamic random access memory (DRAM) cells, need to be refreshed from time-to-time to restore leaking charge and thus maintain a logic state therein. Conventionally, a DRAM refresh process is initiated by a processor or controller coupled to the memory device by supplying an appropriate control signal to a command or control interface of the memory device. More recently, DRAMs hide some forms of refresh from the processor. hi contrast to dynamic memory devices that require periodic refreshing of the memory cells, static memory devices that do not require refreshing of the memory cells have also become commonplace. However, static random access memory (SRAM) devices require more transistors and circuitry to maintain the stored charge. Because of the additional circuitry and the increased area associated therewith, design tradeoffs are frequently undertaken to determine an appropriate form of memory for a system. One developing form of a hybrid memory device has become known as a pseudo static random access memory (PSRAM) device. Accordingly, a PSRAM device includes desirable characteristics of both DRAM devices and SRAM devices, namely, the low cost and large capacity of a DRAM device with the simplified interface and integration of an SRAM device. The PSRAM device provides an improved memory cell density by employing higher density dynamic memory cells but also requires periodic refreshing in order to maintain the stored charge at levels sufficient to determine the logic state stored therein.
To accommodate these refresh requirements, PSRAM devices incorporate refresh circuitry which is "hidden" within the memory device and thus relieves the system designer of the burden of programming a controller or processor to periodically execute the refresh process. This hidden-refresh process within PSRAM devices must be periodically performed within the PSRAM device and requires the use of an appreciable amount of power delivered to the PSRAM device for executing the necessary refresh operation. Because power management is generally of great importance for systems that integrate memory devices, there is a need to provide an improved power conservation methodology for systems that integrate memory devices that utilize hidden-refresh techniques.
DISCLOSURE OF INVENTION
The present invention, in exemplary embodiments, relates to a system and method for modifying a hidden-refresh rate for dynamic memory cells. One embodiment of the present invention comprises a method for modifying a hidden-refresh rate of dynamic data in a memory device. A control signal identifying a request from a processor is monitored at the memory device and a hidden-refresh of dynamic data within the memory device is performed at a first refresh rate when the control signal is asserted. The dynamic data is refreshed at a second refresh rate when the control signal is deasserted for a predetermined duration. m another embodiment of the present invention, a method for refreshing a memory device configured for hidden-refresh is provided. The method includes generating a hidden-refresh clock signal and asserting a refresh pulse when a quantity of cycles of the refresh clock signal equals a count corresponding to a first refresh rate. Addresses corresponding to an array of dynamic memory cells are generated in response to the refresh pulse. The array of dynamic memory cells identified by the address are refreshed. The count corresponding to assertion of the refresh pulse is altered to a second refresh rate when the control signal received at the memory device is deasserted for a predetermined duration.
In a further embodiment of the present invention, a hidden-refresh controller is provided. The hidden-refresh controller includes a hidden-refresh oscillator configured to generate a refresh clock and a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count. The hidden-refresh controller further includes a hidden-refresh address counter configured to generate addresses corresponding to an array of dynamic memory cells in response to the refresh pulse. A mode detector is configured to modify a first refresh rate of the array of dynamic memory cells to a second refresh rate when a control signal received at the mode detector is deasserted for a predetermined duration.
In yet another embodiment of the present invention, a memory device including an array of dynamic memory cells and a hidden-refresh controller is provided. The hidden- refresh controller couples to the array of dynamic memory cells during a hidden-refresh of the array of dynamic memory cells. The hidden-refresh controller is further configured to monitor a control signal identifying a request from a processor at the memory device and refresh the dynamic data at a first refresh rate when the control signal is asserted. The hidden-refresh controller is further configured to refresh the dynamic data at a second refresh rate when the control signal is deasserted for a predetermined duration.
In yet a further embodiment of the present invention, an electronic system comprising an input device, an output device, a memory device, and processor device operably coupled to the input, output, and memory devices is provided. The memory device includes a memory array of dynamic memory cells and a hidden-refresh controller. The hidden-refresh controller includes a hidden-refresh oscillator configured to generate a refresh clock and a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count. The hidden- refresh controller further includes a hidden-refresh address counter configured to generate addresses corresponding to an array of dynamic memory cells in response to the refresh pulse. A mode detector is configured to modify a first refresh rate of the array of dynamic memory cells to a second refresh rate when a control signal received at the mode detector is deasserted for a predetermined duration.
BRIEF DESCRIPTION OF DRAWINGS
In the drawings, which illustrate what is currently considered to be the best mode for carrying out the invention:
, FIG. 1 is a functional block diagram of a system, including a processor and a memory device, that utilizes a hidden-refresh methodology, in accordance with an embodiment of the present invention;
FIG. 2 is a flowchart of a mode detector for determining a functional state or mode of a memory device incorporating hidden-refresh techniques, in accordance with an embodiment of the present invention;
FIG. 3 is a memory device mode detector configured according to the flowchart of FIG. 4 to set a hidden-refresh mode of a memory device, in accordance with an embodiment of the present invention; FIG. 5 is a memory device mode detector configured according to the flowchart of FIG. 6 to set a hidden-refresh mode of a memory device, in accordance with another embodiment of the present invention;
FIG. 7 is a memory device mode detector configured according to the flowchart of FIG. 8 to set a hidden-refresh mode of a memory device, in accordance with a further embodiment of the present invention;
FIG. 9 is a block diagram of an electronic system including a memory device configured with the hidden-refresh circuitry described herein, in accordance with yet another embodiment of the present invention; and FIG. 10 is a diagram of a semiconductor wafer including a memory device configured with the hidden-refresh circuitry described herein, in accordance with yet a further embodiment of the present invention.
BEST MODE(S) FOR CARRYING OUT THE INVENTION Referring in general to the following description and accompanying drawings, various aspects of the present invention are illustrated to show its structure and method of operation. Common elements of the illustrated embodiments are designated with like numerals. It should be understood the figures presented are not meant to be illustrative of actual views of any particular portion of the actual structure or method, but are merely idealized representations which are employed to more clearly and fully depict the present invention.
FIG. 1 is a functional block diagram of a system 200 including a processor 202 coupled to a memory device 204. The memory device 204 includes a hidden-refresh controller 206 for performing refresh operations and for adjusting the refresh rate according to a detected functional state of the memory device in relation to the processor 202. In operation, the hidden-refresh controller 206 initiates a hidden-refresh operation upon the dynamic storage elements (e.g., dynamic memory cells) on aperiodic basis with the period being adjusted based upon the detected functional state of the memory device. Altering the hidden-refresh period or interval enables the memory device to consume less power when conditions are conducive to adequate data retention at a lengthened refresh period. While the present embodiments are described with reference to two memory device functional modes, namely an "active mode" and a "self-refresh mode," the invention is not so limiting. Those of ordinary skill in the art appreciate that various gradations of refresh rates or periods may be defined depending upon various factors including processor-to-memory device access frequencies, power levels, power transients, memory device fabrication process variations and techniques, as well as other conditions known and appreciated by those of ordinary skill in the art. By way of example, and not limitation, the memory device 204 in FIG. 1 may be configured as a pseudo static random access memory (PSRAM) device configured as a dynamic random access memory (DRAM) device utilizing a hidden-refresh methodology. While one exemplary embodiment as described herein is drawn to a PSRAM device, the general principles described herein are applicable to any memory device containing memory cells that need charge replenishment through refreshing techniques (i.e., memory cells that store dynamic data including DRAMs, SDRAMs, SLDRAMs and RDRAMs). hi the following description, certain details are set forth to provide a sufficient understanding of the various embodiments of the invention. Those of ordinary skill in the art will appreciate that the invention and its various embodiments may be practiced through the use of substitution of circuits and logic with programming methodologies coupled with program-executing circuitry. Additionally, the various embodiments of the present invention may be practiced without certain of the details as provided. Furthermore, well known circuits, control signals, timing protocols and other software operations are not shown herein in detail or have been entirely omitted in order to avoid unnecessarily obscuring elements of the various embodiments of the present invention.
System 200 includes a processor 202 which applies addresses to an address decode logic 208 over an address bus ADDR. Typically, the address decode logic 208 decodes a row address RA and a bank address BA which are applied to row address multiplexer 210 and bank control logic 212, respectively. The row address multiplexer 210 applies either the row address RA received from the address decode logic 208 or a refresh row address RFRA received from the hidden-refresh controller 206 to a plurality of row address latch and decoder circuits 214A-D. The bank control logic 212 activates the row address latch and decoder circuit 214A-D corresponding to either the received bank address BA or a refresh bank address RFBA from the hidden-refresh controller 206, and the activated row address latch and decoder circuit latches that decoded the received row address. In response to the decoded row addresses, the activated row address latch and decoder 214A-D applies various control signals to a corresponding memory bank or array 216A-D to thereby activate a row of memory cells corresponding to the decoded row address. The data in the memory cells in the accessed row is sensed and stored in sense amplifiers coupled to the memory bank or array 216A-D, which also refreshes the accessed memory cells as previously described. Similarly during a refresh process, the row address multiplexer 210 applies the refresh row address RFRA to the row address latch and decoders 214A-D and the bank control logic 212 uses the refresh bank address RFBA when the memory device 204 performs a hidden-refresh of the memory cells within memory bank or array 216A-D.
As stated, address decode logic 208 decodes row and bank addresses RA, BA, and a column address CA from the address received on address bus ADDR. Address decode logic 208 may provide the column address CA to a column address counter and latch circuit 218 which, in turn, latches column address and applies the latch column address to a plurality of column decoders 220A-D. The bank control logic 212 activates the column decoder 220A-D corresponding to the received bank address BA, and the activated column decoder decodes the column address CA from the counter and latch circuit 218. Depending upon the operational mode of memory device 204, the counter and latch circuit 218 may either directly apply the latched column address to the decoders 220 A-D, or may apply a sequence of column addresses to the decoders starting at the column address CA provided by the address decode logic 208. Li response to the column address from the counter and latch circuit 218, the activated column decoder 220A-D applies decode and control signals to an I/O gating and data masking circuit 222 which, in turn, accesses memory cells corresponding to the decoded column address in the activated row of memory cells in the array 216A-D being accessed.
Data being read during a read operation from the activated memory bank or array 216A-D may be coupled through the I/O gating and data masking circuit 222 to a read latch 224. The circuit 222 may supply N bits of data to the read latch 224, which may then apply two N/2 bit words to a multiplexer 226. A data driver circuit 228 sequentially receives the N/2 bit words from the multiplexer 226 and also receives a data strobe signal DQS from a strobe signal generator 230 and a delayed clock signal CLKDEL from a delayed-lock loop (DLL) circuit 232. The DQS signal has the same frequency as the CLK signal and is used by the processor 202 in latching data from the memory device 204 during read operations. In response to the delayed clock signal CLKDEL, the data driver circuit 228 sequentially outputs the received N/2 bit words as corresponding data words DQ that, in a dual data rate (DDR) configuration, are synchronized with the rising and falling edges of the CLK signal, and also outputs the data strobe signal DQS having rising and falling edges in synchronism with the rising and falling edges of the CLK signal. Each data word DQ and the data strobe signal DQS collectively define a data bus DATA coupled to the processor 202 which, during read operations, latches the each N/2 bit DQ word on the DATA bus responsive to the data strobe signal DQS.
The processor 202 during data write operations applies N/2 bit data words DQ, the strobe signal DQS on the data bus DATA. The data receiver circuit 234 receives each DQ word and applies these to an input register 236 that is clocked by the DQS signal, hi a dual data rate (DDR) example and in response to the rising edge of the DQS signal, input register 236 latches a first N/2 bit DQ word and in response to a falling edge of the DQS signal, the input register latches the corresponding N/2 bit DQ word. Input register 236 provides the two latched N/2 bit DQ words as an N-bit word to a write FIFO and driver circuit 238, which clocks the applied DQ word into the write FIFO and driver circuit in response to the DQS signal. The DQS word is clocked out of the write FIFO and driver circuit 238 in response to the CLK signal, and then is applied to the I/O gating and masking circuit 222. The I/O gating and masking circuit 222 transfers the DQ word to the accessed memory cells in the active array 216A-D. While the present illustration is drawn to support a dual data rate, the various embodiments also contemplate lesser and greater data rates.
Control logic 240 receives a plurality of command and clocking signals from a processor 202 over a control bus CONT, and generates a plurality of control and timing signals to control the various memory device components 206-238 during operation of the memory device 204. The command signals may include a chip enable signal CE*, a write enable signal WE*, an output enable signal OE*, a lower byte enable signal LB*, an upper byte enable signal UB*, a clock signal CLK, and may optionally include other control signals such as a sleep enable signal ZZ*. One or more of the aforementioned signals may further include corresponding complementary signals, with the "*" designating a signal as being active when asserted low. When interfaced, processor 202 drives the command signals CE*, WE* to values corresponding to a particular command such as a read or write operation. In response to the clock signal CLK, the control logic circuit 240 latches and decodes an applied command and generates a sequence of control signals that control various components in the memory device to execute the function of the applied command. By way of example, and not limitation, the control logic circuit 240 latches command and address signals at positive edges of the CLK signal, while the input registers 236 and data driver circuits 228 may transfer data into and from the memory device 204 in response to either one or both edges of the data strobe signal DQS. When data transfer occurs on both edges of the clock signals CLK, memory device 204 may be referred to as a double-data-rate (DDR) device with data being transferred to and from the device at double the rate of a conventional SRAM, which transfers data at a rate corresponding to the frequency of the applied clock signal.
As previously stated, PSRAM memory devices generally find application to low- power portable applications while providing high density memory storage. Memory device 204 performs on-chip refresh operations, generally noted herein as a hidden-refresh of the dynamic memory cells within memory bank or memory array 216A-D. The hidden-refresh process performed by hidden-refresh controller 206 requires no additional support from a system memory controller. Furthermore, in low-power portable applications, special attention is given to operational power consumption in the memory device during the hidden-refresh process. The hidden-refresh controller 206 detects the need for refreshing the data stored within the memory banks or array 216A-D to prevent the loss of the data logic states due to leakage currents associated with dynamic memory elements. Generally, the hidden-refresh controller 206 includes a hidden-refresh oscillator 242 configured to generate a hidden-refresh clock signal RFCLK. The RFCLK signal provides a reference frequency for counting a quantity of clocks to determine a refresh interval or period. Hidden-refresh controller 206 further includes a hidden-refresh refresh counter 244 coupled to the RFCLK signal of the hidden-refresh oscillator 242. Hidden-refresh counter 244 counts a specific quantity of cycles of the RFCLK signal to determine when to assert a REFRESH PULSE signal. A refresh period or rate is determined for maintaining the stored charge within the memory bank or array 216A-D. The frequency of the REFRESH PULSE signal is a function of a defined threshold COUNT for each of the modes defined within the hidden-refresh counter 244. Hidden- refresh controller 206 further includes a hidden-refresh address counter 246 configured to generate refresh addresses (e.g., refresh row addresses RFRA and refresh bank addresses RFBA) in response to a REFRESH PULSE. The refresh counter 244 is configurable by a mode detector 248 which determines if the memory device 204 is in one of at least two hidden-refresh modes, namely (i) an active mode wherein data is being or has recently been transferred between processor 202 and memory elements within the memory bank or array 216A-D or (ii) a self-refresh mode wherein an inactivity duration of the exchange of information between processor 202 and memory elements of the memory array has been detected. The memory device 204, when actively exchanging data with the processor 202, defaults to an active mode of the hidden-refresh process. The active mode of the hidden-refresh process provides for a more frequent execution of the refresh operation to mitigate data loss due to conditions such as voltage bumps or transients, moving inversions through the array, or long RAS low conditions that induce charge leakage in the dynamic memory cell.
To place the memory device 204 in a hidden-refresh mode of operation, the hidden-refresh counter 244 detects achievement of a COLfNT quantity of RFCLK signals corresponding to the current hidden-refresh mode (e.g., active mode or self-refresh mode) which causes the commencement of a hidden-refresh operation. In response, the hidden- refresh controller 206 applies control signals to the row address multiplexer 210 and the bank control logic 212 which cause the circuits to utilize the refresh row address RFRA and refresh bank address RFBA from the hidden-refresh controller 206 to sequentially access each row of memory cells in the memory array 216A-D and thereby refresh the memory cells. The hidden-refresh controller 206 controls the refresh rate at which the memory cells in the arrays 216A-D are refreshed as a function of the determined memory device functional mode (e.g., active mode or self-refresh mode) as determined by mode detector 248 within hidden-refresh controller 206.
As stated, the hidden-refresh controller 206 includes a mode detector 243 which monitors one or more signals within memory device 204 to determine conditions that are conducive to the various functional modes. As stated, it is desirable to conserve power within system 200, therefore, when mode detector 243 determines conditions under which the hidden-refresh rate of the memory cells of memory array 216A-D may be reduced and still retain data integrity, mode detector 243 signals a change in the hidden-refresh mode from the higher or more frequent refresh rate "active mode" to the less frequent refresh rate of "self-refresh mode." When the mode detector 243 determines a specific hidden- refresh mode, the mode detector 243 asserts a MODE signal to the hidden-refresh counter 244 to utilize a corresponding value of COUNT for determining when to assert the REFRESH PULSE signal.
In operation, upon the generation of a REFRESH PULSE signal from the hidden- refresh counter 244, the hidden-refresh controller 206 applies control signals causing the row address multiplexer 210 and the bank control logic 212 to utilize the refreshed row address RFRA and refresh bank addresses RFBA, respectively. The hidden-refresh oscillator 242 may apply the refresh clock signal RFCLK to clock the hidden-refresh counter 246 which in turn sequentially generates the refresh row addresses RFRA and refresh bank addresses RFBA. The sequentially generated refresh row addresses RFRA are applied through the multiplexer 210 and latched and decoded by the activated row address latch and decoder circuit 214A-D, with the bank control logic circuit 212 activating the circuit 214A-D corresponding to the refresh bank address RFBA. The hidden-refresh controller 206 generates a given refresh bank address RFBA and then generates refresh row addresses RFRA to sequentially activate all rows in the memory array 216A-D corresponding to the bank address, and thereafter generates a new bank address and activates each row in the newly selected memory address, and so on for each memory array. In this manner, the refresh controller 206 sequentially activates rows of memory cells in the arrays 216A-D to thereby refresh the memory cells. The refresh rate of the memory cells in the arrays 216A-D is determined by the rate at which the refresh counter 244 reaches the currently defined COUNT corresponding to the current functional refresh mode as conveyed to the hidden-refresh counter 244 by the MODE signal.
Mode detector 248 may be configured according to one or more of the embodiments of the present invention as illustrated with reference to FIGS. 3-8. Generally, mode detector 243 functions according to the flowchart of FIG. 2. In FIG. 2, the mode detector 243 (FIG. 1) monitors various signals to detect 302 specific conditions under which one refresh functional mode should be defined. The mode is identified 304 as either an active mode where the refresh rate is performed more frequently 312, or a self-refresh mode where the refresh rate may be performed less frequently 308 in order to contribute to the conservation of power in system 200 (FIG. 1). The conditions that define the various modes are continually monitored to determine when the modes may be changed to conserve power or when the modes should be changed in order to preserve data integrity. FIG. 3 illustrates a logic block of a hidden-refresh mode detector functioning according to the flow chart of FIG. 4, in accordance with an embodiment of the present invention. Referring to both FIGS. 3 and 4, the hidden-refresh mode of either active or self-refresh is determined from analyzing a control signal, such as the chip enable CE* signal, to determine a state and duration associated therewith. In the present embodiment, if the chip enable CE* remains unasserted for more than a predetermined delay, then the MODE signal will indicate the memory device 204 (FIG. 1) should be configured in a self-refresh mode designating conditions conducive for stretching or lengthening the hidden-refresh duration. By way of implementation, the mode detector 320 includes an element 322 that may be configured in various manners including a resettable delay element that propagates the CE* signal until it arrives at the output of the delay element. In another configuration, element 322 may be configured as a resettable timer or counter that compares a count against a threshold or other value until the count equals the threshold and the MODE signal designates the determined hidden-refresh mode. FIG. 4 is the corresponding flowchart for detecting the mode, in accordance with the present embodiment of the invention. A hidden-refresh mode detector 320 (FIG. 3) evaluates 330 the current mode. If the current mode is active, then the state of chip enable CE* is determined 332. If chip enable CE* is asserted, this is an indication that ongoing accesses to the memory device 204 (FIG. 1) are being performed by the processor 202 (FIG. 1). Accordingly, power transients and other memory array access conditions demand a more frequent refresh of the memory cells and the MODE remains set to active and processing returns to evaluating the functional mode and any forthcoming inactivity in the memory device as indicated by an unasserted control signal, such as the chip enable CE* signal. When the mode is evaluated 330 and determined to be self-refresh, then the state of chip enable CE* is determined 334. If chip enable CE* remains unasserted, this is an indication of ongoing or sustained inactivity between the memory device 204 and the processor 202. Accordingly, any power transients and other memory array access conditions are diminished and a less frequent refresh of the memory cells remains adequate for retention of the resident logic states resulting in the MODE remaining set to self-refresh with processing returning to an evaluation of the mode and any forthcoming activity in the memory device as indicated by, for example, an asserted chip enable CE* signal. Determination 334 of an asserted chip enable CE* signal indicates that accesses to the memory device 204 have been resumed and are being performed by processor 202. Accordingly, power transients and other memory array access conditions likely require a more frequent refresh of the memory cells and, therefore, the MODE is set 336 to indicate an active mode and processing returns to evaluating 330 the mode and a determination 332 of any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
When the mode is evaluated 330 and determined to be active and the state of chip enable CE* is determined 332 to be unasserted, then the element 322 (FIG. 3) is reset 338 through clearing of the delay line, resetting a duration timer/counter or other similar duration measuring element. The achievement of a duration or threshold of the element 322 is measured 340. While the threshold is unachieved, the chip enable CE* signal is continuously monitored 342 and while the chip enable CE* signal remains unasserted, processing continues to return to measure 340 the timer/counter element 322 against the threshold. As stated, while measuring 340 for the achievement of the threshold, the chip enable CE* signal is monitored 342. If the chip enable CE* signal becomes asserted, then the MODE is set 344 to indicate the active mode and processing returns to evaluating 330 the mode and for determining 332 any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal. When the achievement of a duration or threshold of the element 322 is measured 340 and the threshold is achieved, the MODE is set 346 to indicate the self refresh mode and processing returns to evaluating 330 the mode and for determining 334 any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal. While the present embodiment has utilized the chip enable CE* signal as an indicator of activity and inactivity between the processor 202 (FIG. 1) and the memory device 204 (FIG. 1), other control or address signals maybe employed to indicate interaction or the lack thereof between the processor 202 and the memory device 204. Such modifications and adaptations are considered to be within the scope of the present embodiment of the invention.
FIG. 5 illustrates a logic block of a hidden-refresh mode detector functioning according to the flowchart of FIG. 6, in accordance with another embodiment of the present invention. Referring to both FIGS. 5 and 6, the functional refresh mode of either active mode or self-refresh mode is determined from analyzing the REFRESH PULSE signal to determine a pulse and consecutive occurrences of the pulse. In the present embodiment, if the refresh pulse counter 422 detects a series of consecutive occurrences of the REFRESH PULSE signal, then the MODE signal will indicate the memory device 204 (FIG. 1) should be configured in a self-refresh mode designating conditions conducive for stretching or lengthening the hidden-refresh duration. By way of implementation, the mode detector 420 includes a refresh pulse counter 422 that may be configured in various manners including as a series of resettable latches that are clocked to propagate the chip enable CE* signal until the signal arrives at the output of the refresh pulse counter 422.
FIG. 6 is the corresponding flowchart for detecting the mode, in accordance with the present embodiment of the invention. A hidden-refresh mode detector 420 (FIG. 5) evaluates 430 the current mode. If the current mode is active, then the state of chip enable CE* signal is determined 432. If chip enable CE* signal is asserted, this is an indication that ongoing accesses to the memory device 204 (FIG. 1) are being performed by the processor 202 (FIG. 1). Accordingly, power transients and other memory array access conditions may demand a more frequent refresh of the memory cells. Therefore, the MODE remains set to indicate the active mode and processing returns to evaluating the mode and any forthcoming inactivity in the memory device. Inactivity in the memory device may be indicated by an unasserted chip enable CE* signal resulting in a release of the latches of refresh pulse counter 422 (FIG. 5) from a reset state.
When the mode is evaluated 430 and determined to be self-refresh, then the state of the chip enable CE* signal is determined 434. If the chip enable CE* signal remains unasserted indicating ongoing inactivity between the memory device 204 and the processor 202, the affect of power transients and other memory array access conditions are diminished and a less frequent refresh of the memory cells may be adequate for retention of the resident logic states. Accordingly, the MODE remains set to indicate the self- refresh mode with processing returning to evaluate the mode and any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal. Determination 434 of an asserted chip enable CE* signal indicates that accesses to the memory device 204 have been resumed and are being performed by processor 202. Accordingly, power transients and other memory array access conditions likely require a more frequent refresh of the memory cells and, therefore, and the MODE is set 436 to indicate an active mode and processing returns to evaluating 430 the mode and a determination 432 of any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
When the mode is determined 430 to be active and the state of chip enable CE* is determined 432 to be unasserted, then the refresh pulse counter 422 (FIG. 5) is released from reset 438 (i.e., the latches are released from being held reset and therefore inhibiting propagation of a signal). The propagation of an unasserted chip enable CE* signal through the series of latches within refresh pulse counter 422 (FIG. 5) occurs unless the chip enable CE* signal becomes asserted and causes the suspension of propagation through the latches. The chip enable CE* signal is monitored 440 and if the chip enable CE* signal becomes asserted, then the MODE remains in the active state and processing returns to evaluating 430 the mode and for determining 432 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal. If the chip enable CE* signal remains unasserted, then detection 442 of a first refresh pulse is performed. If the first refresh detection pulse is not detected, then processing returns to monitor 440 for assertion of the chip enable CE* signal causing the MODE to continue indicating the active mode and processing returns to evaluate 430 the mode and to determine 432 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal. When a first refresh pulse is detected 442, the process of monitoring 444 for the assertion of the chip enable CE* signal and the detection 446 continues. It should be noted that in the block diagram of FIG. 5 and in the flowchart of FIG. 6, two distinct latches and two distinct monitor chip enable/detect refresh pulse steps sequences are depicted. It should be appreciated that any quantity of consecutive refresh pulse counts may be selected before conditions are deemed acceptable for transitioning from an active mode of hidden-refresh to a self-refresh mode. The quantity of two is merely illustrative and not to be considered as limiting.
When the unasserted chip enable CE* signal has propagated through refresh pulse counter 422 (FIG. 5), the MODE is set 448 to indicate the self-refresh mode and processing returns to evaluating 430 the mode and for determining 434 any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal.
As stated, while the present embodiment has utilized the chip enable CE* signal as an indicator of activity/inactivity between the processor 202 (FIG. 1) and the memory device 204 (FIG. 1), other control or address signals may be employed to indicate interaction or the lack thereof between the processor 202 and the memory device 204. Such modifications and adaptations are considered to be within the scope of the present embodiment of the invention. FIG. 7 illustrates a logic block of a hidden-refresh mode detector functioning according to the flowchart of FIG. 8, in accordance with an embodiment of the present invention. Referring to both FIGS. 7 and 8, the functional refresh mode of either active mode or self-refresh mode is determined from analyzing a refresh complete signal, an example of which is a CARRY OUT signal from the hidden-refresh address counter 246 (FIG. 1) to determine consecutive occurrences of a completed refresh operation. In the present embodiment, if a refresh complete counter 522 detects a series of consecutive occurrences of the CARRY OUT signal, then the MODE signal will indicate the memory device 204 (FIG. 1) should be configured in a self-refresh mode designating conditions conducive for stretching or lengthening the hidden-refresh duration. By way of implementation, the mode detector 520 includes a refresh complete counter 522 that may be configured in various manners including as a series of resettable latches that are clocked to propagate the chip enable CE* signal until the signal arrives at the output of the refresh complete counter 522.
FIG. 8 is the corresponding flowchart for detecting the mode, in accordance with the present embodiment of the invention. A hidden-refresh mode detector 520 (FIG. 7) evaluates 530 the current mode. If the current mode is active, then the state of chip enable CE* signal is determined 532. If chip enable CE* signal is asserted, this is an indication that ongoing accesses to the memory device 204 (FIG. 1) are being performed by the processor 202 (FIG. 1). Accordingly, power transients and other memory array access conditions may demand a more frequent refresh of the memory cells. Therefore, the MODE remains set to indicate the active mode and processing returns to evaluating the mode and any forthcoming inactivity in the memory device. Inactivity in the memory device may be indicated by an unasserted chip enable CE* signal resulting in a release of the latches of refresh complete counter 522 (FIG. 7) from a reset state. When the mode is evaluated 530 and determined to be self-refresh, then the state of the chip enable CE* signal is determined 534. If the chip enable CE* signal remains unasserted indicating ongoing inactivity between the memory device 204 and the processor 202, the affect of power transients and other memory array access conditions are diminished and a less frequent refresh of the memory cells maybe adequate for retention of the resident logic states. Accordingly, the MODE remains set to indicate the self- refresh mode with processing returning to evaluate the mode and any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal. Determination 534 of an asserted chip enable CE* signal indicates that accesses to the memory device 204 have been resumed and are being performed by processor 202. Accordingly, power transients and other memory array access conditions likely require a more frequent refresh of the memory cells and, therefore, the MODE is set 536 to indicate an active mode and processing returns to evaluating 530 the mode and a determination 532 of any forthcoming inactivity in the memory device as indicated, for example, by an unasserted chip enable CE* signal.
When the mode is evaluated 530 and determined to be active and the state of chip enable CE* is determined 532 to be unasserted, then the refresh complete counter 522 (FIG. 7) is released from reset 538 (i.e., the latches are released from being held reset and therefore inhibiting propagation of a signal). The propagation of an unasserted chip enable CE* signal through the series of latches within refresh complete counter 522 (FIG. 5) occurs unless the chip enable CE* signal becomes asserted and causes the suspension of propagation through the latches. The chip enable CE* signal is monitored 540 and if the chip enable CE* signal becomes asserted, then the MODE remains in the active state and processing returns to evaluating 530 the mode and for determining 532 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal. If the chip enable CE* signal remains unasserted, then detection 542 of a first refresh complete, namely a CARRY OUT, signal is performed. If the first CARRY OUT signal is not detected, then processing returns to monitor 540 for assertion of the chip enable CE* signal causing the MODE to continue indicating the active mode and processing returns to evaluate 530 the mode and to determine 532 any forthcoming inactivity in the memory device as indicated by an unasserted chip enable CE* signal.
When a first CARRY OUT signal is detected 542, the process of monitoring 544 for the assertion of the chip enable CE* signal and the detection 546 continues. It should be noted that in the block diagram of FIG. 7 and in the flowchart of FIG. 8, two distinct latches and two distinct monitor chip enable/detect CARRY OUT steps sequences are depicted. It should be appreciated that any quantity of consecutive CARRY OUT counts may be selected before conditions are deemed acceptable for transitioning from an active mode of hidden-refresh to a self-refresh mode. The quantity of two is merely illustrative and not to be considered as limiting.
When the unasserted chip enable CE* signal has propagated through refresh complete counter 522 (FIG. 7), the MODE is set 548 to indicate the self-refresh mode and processing returns to evaluating 530 the mode and for determining 534 any forthcoming activity in the memory device as indicated by an asserted chip enable CE* signal.
As stated, while the present embodiment has utilized the chip enable CE* signal as an indicator of activity/inactivity between the processor 202 (FIG. 1) and the memory device 204 (FIG. 1), other control or address signals maybe employed to indicate interaction or the lack thereof between the processor 202 and the memory device 204. Such modifications and adaptations are considered to be within the scope of the present embodiment of the invention.
FIG. 9 is a block diagram of an electronic system including a memory device configured in accordance with an embodiment of the present invention. An electronic system 550 includes an input device 552, an output device 554, a processor 202, and a memory device 204 incorporating a hidden-refresh controller 206, as described above with reference to FIGS. 1-8.
As shown in FIG. 10, the memory device 204 of FIGS. 1-8 may be fabricated on a semiconductor wafer 560. Of course, it should be understood that semiconductor substrates other than a semiconductor wafer also fall within the scope of the present invention, including, for example, Silicon-On-Sapphire (SOS) substrates and Silicon-On- Glass (SOG) substrates.
Although the present invention has been described with reference to particular embodiments, the invention is not limited to these described embodiments. Rather, the invention is limited only by the appended claims, which include within their scope all equivalent devices or methods that operate according to the principles of the inventions as described.

Claims

CLAIMSWhat is claimed is:
1. A method for modifying a hidden-refresh rate of dynamic data in a memory device, comprising: monitoring a control signal at the memory device, the control signal identifying a request from a processor; refreshing the dynamic data at a first refresh rate when the control signal is asserted; and refreshing the dynamic data at a second refresh rate when the control signal is deasserted for a predetermined duration.
2. The method of claim 1, wherein the control signal is a chip enable signal initiated by the processor.
3. The method of claim 1 , wherein the first refresh rate is more frequent than the second refresh rate.
4. The method of claim 1, wherein monitoring further comprises timing the control signal when deasserted against a duration threshold to determine the predetermined duration.
5. The method of claim 1 , wherein monitoring further comprises measuring a quantity of refresh pulses while the control signal is deasserted to determine the predetermined duration.
6. The method of claim 1 , wherein monitoring further comprises measuring a quantity of refresh complete signals while the control signal is deasserted to determine the predetermined duration.
7. A method for refreshing a memory device configured for hidden-refresh, comprising: generating a hidden-refresh clock signal; asserting a refresh pulse when a quantity of cycles of the refresh clock signal equals a count corresponding to a first refresh rate; generating addresses corresponding to an array of dynamic memory cells in the memory device in response to the refresh pulse; refreshing the array of dynamic memory cells identified by the addresses; and altering the count corresponding to a second refresh rate when a control signal received at the memory device is deasserted for a predetermined duration.
8. The method of claim 7, wherein the control signal is a chip enable signal initiated by a processor.
9. The method of claim 7, wherein the first refresh rate is more frequent than the second refresh rate.
10. The method of claim 7, wherein altering further comprises timing the control signal when deasserted against a duration threshold to determine the predetermined duration.
11. The method of claim 7, wherein altering further comprises measuring a quantity of consecutive occurrences of the refresh pulse while the control signal is deasserted to determine the predetermined duration.
12. The method of claim 7, wherein monitoring further comprises measuring a quantity of consecutive occurrences of refreshing the array while the control signal is deasserted to determine the predetermined duration.
13. A hidden-refresh controller, comprising: a hidden-refresh oscillator configured to generate a refresh clock; a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count; a hidden-refresh address counter configured to generate addresses corresponding to an array of dynamic memory cells in response to the refresh pulse; and a mode detector configured to modify a first refresh rate of the array of dynamic memory cells to a second refresh rate when a control signal received at the mode detector is deasserted for a predetermined duration.
14. The hidden-refresh controller of claim 13, wherein the control signal is a chip enable signal received at the hidden-refresh controller.
15. The hidden-refresh controller of claim 13, wherein the first refresh rate is more frequent than the second refresh rate.
16. The hidden-refresh controller of claim 13, wherein the predetermined duration is determined by timing the control signal when deasserted against a duration threshold.
17. The hidden-refresh controller of claim 13, wherein the predetermined duration is determined by measuring a quantity of consecutive occurrences of the refresh pulse while the control signal is deasserted.
18. The hidden-refresh controller of claim 13, wherein the predetermined duration is determined by measuring a quantity of consecutive occurrences of refreshing the array while the control signal is deasserted.
19. A memory device, comprising: an array of dynamic memory cells; and a hidden-refresh controller couplable to the array of dynamic memory cells during a hidden-refresh of the array of dynamic memory cells, the hidden-refresh conn configured to monitor a control signal identifying a request from a processor a memory device, refresh the dynamic data a first refresh rate when the control signal is asserted, and refresh the dynamic data at a second refresh rate when th< control signal is deasserted for a predetermined duration.
20. The memory device of claim 19, wherein the hidden-refresh controller includes: a hidden-refresh oscillator configured to generate a refresh clock; a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count; a hidden-refresh address counter configured to generate addresses corresponding to the array of dynamic memory cells in response to the refresh pulse; and a mode detector configured to modify the first refresh rate of the array of dynamic memory cells to the second refresh rate when the control signal received at the mode detector is deasserted for the predetermined duration.
21. The memory device of claim 20, wherein the control signal is a chip enable signal received at the hidden-refresh controller.
22. The memory device of claim 20, wherein the first refresh rate is more frequent than the second refresh rate.
23. The memory device of claim 20, wherein the predetermined duration is determined by timing the control signal when deasserted against a duration threshold.
24. The memory device claim 20, wherein the predetermined duration is determined by measuring a quantity of consecutive occurrences of the refresh pulse while the control signal is deasserted.
25. The memory device of claim 20, wherein the predetermined duration is determined by measuring a quantity of consecutive occurrences of refreshing the array while the control signal is deasserted.
26. An electronic system comprising an input device, an output device, a memory device, and processor device operably coupled to the input, output, and memory devices, the memory device including an array of dynamic memory cells and a hidden- refresh controller, comprising: a hidden-refresh oscillator configured to generate a refresh clock; a refresh counter configured to count a quantity of cycles of the refresh clock and assert a refresh pulse when the quantity equals a defined count; a hidden-refresh address counter configured to generate addresses corresponding to an array of dynamic memory cells in response to the refresh pulse; and a mode detector configured to modify a first refresh rate of the array of dynamic memory cells to a second refresh rate when a control signal received at the mode detector is deasserted for a predetermined duration.
27. The electronic system of claim 26, wherein the control signal is a chip enable signal received at the hidden-refresh controller.
28. The electronic system of claim 26, wherein the first refresh rate is more frequent than the second refresh rate.
29. The electronic system of claim 26, wherein the predetermined duration is determined by timing the control signal when deasserted against a duration threshold.
30. The electronic system of claim 26, wherein the predetermined duration is determined by measuring a quantity of consecutive occurrences of the refresh pulse while the control signal is deasserted.
31. The electronic system of claim 26, wherein the predetermined duration is determined by measuring a quantity of consecutive occurrences of refreshing the array while the control signal is deasserted.
32. A semiconductor wafer including a plurality of memory devices, at least one of the plurality of memory devices, comprising: an array of dynamic memory cells; and a hidden-refresh controller operably couplable to the array of dynamic memory cells during a hidden-refresh of the array of dynamic memory cells, the hidden-refresh controller configured to monitor a control signal identifying a request from a processor at the memory device, refresh the dynamic data a first refresh rate when the control signal is asserted, and refresh the dynamic data at a second refresh rate when the control signal is deasserted for a predetermined duration.
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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101640065B (en) * 2008-07-29 2012-07-04 国际商业机器公司 Refresh controller and refresh control method used for embedded DRAM
WO2020131457A1 (en) * 2018-12-21 2020-06-25 Micron Technology, Inc. Methods for activity-based memory maintenance operations and memory devices and systems employing the same
US11604694B2 (en) 2018-12-31 2023-03-14 Micron Technology, Inc. Error correction in row hammer mitigation and target row refresh
US11810610B2 (en) 2018-10-09 2023-11-07 Lodestar Licensing Group Llc Methods for row hammer mitigation and memory devices and systems employing the same
US11837272B2 (en) 2018-08-03 2023-12-05 Lodestar Licensing Group Llc Methods for row hammer mitigation and memory devices and systems employing the same

Families Citing this family (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7532532B2 (en) 2005-05-31 2009-05-12 Micron Technology, Inc. System and method for hidden-refresh rate modification
JP5082727B2 (en) * 2007-09-28 2012-11-28 ソニー株式会社 Storage control device, storage control method, and computer program
JP2009181666A (en) * 2008-01-31 2009-08-13 Sony Corp Semiconductor memory device and operation method thereof
US7990795B2 (en) * 2009-02-19 2011-08-02 Freescale Semiconductor, Inc. Dynamic random access memory (DRAM) refresh
GB0912507D0 (en) * 2009-07-17 2009-08-26 Skype Ltd Reducing processing resources incurred by a user interface
US8612669B1 (en) * 2010-06-28 2013-12-17 Western Digital Technologies, Inc. System and method for performing data retention in solid-state memory using copy commands and validity and usage data
KR102021401B1 (en) * 2012-08-30 2019-11-04 에스케이하이닉스 주식회사 Memory device
US9159397B2 (en) * 2012-12-04 2015-10-13 Micron Technology, Inc. Methods and apparatuses for refreshing memory
US9196347B2 (en) 2013-03-14 2015-11-24 International Business Machines Corporation DRAM controller for variable refresh operation timing
KR102163983B1 (en) * 2013-11-07 2020-10-12 에스케이하이닉스 주식회사 Semiconduct memory device
US9986350B2 (en) 2014-06-27 2018-05-29 Cochlear Limited System and method for improving data integrity and power efficiency
US9490002B2 (en) 2014-07-24 2016-11-08 Rambus Inc. Reduced refresh power
US9607677B2 (en) 2015-03-31 2017-03-28 Micron Technology, Inc. Apparatuses for resetting an address counter during refresh operations
US20170110178A1 (en) * 2015-09-17 2017-04-20 Intel Corporation Hybrid refresh with hidden refreshes and external refreshes
US10490251B2 (en) 2017-01-30 2019-11-26 Micron Technology, Inc. Apparatuses and methods for distributing row hammer refresh events across a memory device
CN112106138B (en) 2018-05-24 2024-02-27 美光科技公司 Apparatus and method for pure time adaptive sampling for row hammer refresh sampling
US10573370B2 (en) 2018-07-02 2020-02-25 Micron Technology, Inc. Apparatus and methods for triggering row hammer address sampling
US10685696B2 (en) 2018-10-31 2020-06-16 Micron Technology, Inc. Apparatuses and methods for access based refresh timing
WO2020117686A1 (en) 2018-12-03 2020-06-11 Micron Technology, Inc. Semiconductor device performing row hammer refresh operation
CN111354393B (en) 2018-12-21 2023-10-20 美光科技公司 Apparatus and method for timing interleaving for targeted refresh operations
US10957377B2 (en) 2018-12-26 2021-03-23 Micron Technology, Inc. Apparatuses and methods for distributed targeted refresh operations
US11615831B2 (en) 2019-02-26 2023-03-28 Micron Technology, Inc. Apparatuses and methods for memory mat refresh sequencing
US11227649B2 (en) 2019-04-04 2022-01-18 Micron Technology, Inc. Apparatuses and methods for staggered timing of targeted refresh operations
US11069393B2 (en) 2019-06-04 2021-07-20 Micron Technology, Inc. Apparatuses and methods for controlling steal rates
US10978132B2 (en) 2019-06-05 2021-04-13 Micron Technology, Inc. Apparatuses and methods for staggered timing of skipped refresh operations
US11302374B2 (en) 2019-08-23 2022-04-12 Micron Technology, Inc. Apparatuses and methods for dynamic refresh allocation
US11302377B2 (en) 2019-10-16 2022-04-12 Micron Technology, Inc. Apparatuses and methods for dynamic targeted refresh steals
US11309010B2 (en) 2020-08-14 2022-04-19 Micron Technology, Inc. Apparatuses, systems, and methods for memory directed access pause
US11380382B2 (en) 2020-08-19 2022-07-05 Micron Technology, Inc. Refresh logic circuit layout having aggressor detector circuit sampling circuit and row hammer refresh control circuit
US11348631B2 (en) 2020-08-19 2022-05-31 Micron Technology, Inc. Apparatuses, systems, and methods for identifying victim rows in a memory device which cannot be simultaneously refreshed
US11557331B2 (en) 2020-09-23 2023-01-17 Micron Technology, Inc. Apparatuses and methods for controlling refresh operations
US11222686B1 (en) 2020-11-12 2022-01-11 Micron Technology, Inc. Apparatuses and methods for controlling refresh timing
US11264079B1 (en) 2020-12-18 2022-03-01 Micron Technology, Inc. Apparatuses and methods for row hammer based cache lockdown
US11914905B1 (en) * 2021-07-15 2024-02-27 Xilinx, Inc. Memory self-refresh re-entry state

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5808952A (en) * 1996-10-28 1998-09-15 Silicon Magic Corporation Adaptive auto refresh
US6134167A (en) * 1998-06-04 2000-10-17 Compaq Computer Corporation Reducing power consumption in computer memory
EP1530218A2 (en) * 2003-11-05 2005-05-11 Fujitsu Limited Semiconductor integrated circuit having temperature detector

Family Cites Families (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS58155596A (en) * 1982-03-10 1983-09-16 Hitachi Ltd Dynamic type mos ram
JP2534757B2 (en) * 1988-07-06 1996-09-18 株式会社東芝 Refresh circuit
JP2928263B2 (en) * 1989-03-20 1999-08-03 株式会社日立製作所 Semiconductor device
JPH04372790A (en) * 1991-06-21 1992-12-25 Sharp Corp Semiconductor memory
US5617551A (en) * 1992-09-18 1997-04-01 New Media Corporation Controller for refreshing a PSRAM using individual automatic refresh cycles
JP3026474B2 (en) * 1993-04-07 2000-03-27 株式会社東芝 Semiconductor integrated circuit
US5446695A (en) * 1994-03-22 1995-08-29 International Business Machines Corporation Memory device with programmable self-refreshing and testing methods therefore
JP3165585B2 (en) * 1994-05-13 2001-05-14 シャープ株式会社 Information processing device
US5848247A (en) * 1994-09-13 1998-12-08 Hitachi, Ltd. Microprocessor having PC card interface
JPH09147554A (en) * 1995-11-24 1997-06-06 Nec Corp Dynamic storage device and its driving method
JPH09306164A (en) * 1996-05-13 1997-11-28 Internatl Business Mach Corp <Ibm> Memory refresh system
US6392948B1 (en) * 1996-08-29 2002-05-21 Micron Technology, Inc. Semiconductor device with self refresh test mode
US5703832A (en) * 1997-02-28 1997-12-30 Etron Technology, Inc. tRAS protection circuit
US6028804A (en) * 1998-03-09 2000-02-22 Monolithic System Technology, Inc. Method and apparatus for 1-T SRAM compatible memory
US6334167B1 (en) * 1998-08-31 2001-12-25 International Business Machines Corporation System and method for memory self-timed refresh for reduced power consumption
US6292869B1 (en) * 1998-08-31 2001-09-18 International Business Machines Corporation System and method for memory scrub during self timed refresh
US6282606B1 (en) * 1999-04-02 2001-08-28 Silicon Aquarius, Inc. Dynamic random access memories with hidden refresh and utilizing one-transistor, one-capacitor cells, systems and methods
JP4743999B2 (en) * 2001-05-28 2011-08-10 ルネサスエレクトロニクス株式会社 Semiconductor memory device
JP4765222B2 (en) * 2001-08-09 2011-09-07 日本電気株式会社 DRAM device
JP4152094B2 (en) * 2001-09-03 2008-09-17 エルピーダメモリ株式会社 Semiconductor memory device control method and semiconductor memory device
US6646942B2 (en) * 2001-10-09 2003-11-11 Micron Technology, Inc. Method and circuit for adjusting a self-refresh rate to maintain dynamic data at low supply voltages
US6625077B2 (en) * 2001-10-11 2003-09-23 Cascade Semiconductor Corporation Asynchronous hidden refresh of semiconductor memory
JP4289825B2 (en) * 2002-03-29 2009-07-01 株式会社ルネサステクノロジ Semiconductor memory device
JP2003317473A (en) * 2002-04-15 2003-11-07 Mitsubishi Electric Corp Semiconductor memory device
JP2003317468A (en) * 2002-04-15 2003-11-07 Mitsubishi Electric Corp Semiconductor memory device
US6795361B2 (en) * 2002-05-06 2004-09-21 Micron Technology, Inc. Low power consumption memory device having row-to-column short
KR100482365B1 (en) * 2002-07-12 2005-04-13 삼성전자주식회사 Refresh control circuits in pseudo sram device and method same
JP4597470B2 (en) * 2002-07-25 2010-12-15 富士通セミコンダクター株式会社 Semiconductor memory
US6721224B2 (en) * 2002-08-26 2004-04-13 Mosel Vitelic, Inc. Memory refresh methods and circuits
US6795364B1 (en) * 2003-02-28 2004-09-21 Monolithic System Technology, Inc. Method and apparatus for lengthening the data-retention time of a DRAM device in standby mode
JP2005285271A (en) * 2004-03-30 2005-10-13 Nec Electronics Corp Semiconductor memory device
US7433996B2 (en) * 2004-07-01 2008-10-07 Memocom Corp. System and method for refreshing random access memory cells
US7158434B2 (en) * 2005-04-29 2007-01-02 Infineon Technologies, Ag Self-refresh circuit with optimized power consumption
US7532532B2 (en) 2005-05-31 2009-05-12 Micron Technology, Inc. System and method for hidden-refresh rate modification

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5808952A (en) * 1996-10-28 1998-09-15 Silicon Magic Corporation Adaptive auto refresh
US6134167A (en) * 1998-06-04 2000-10-17 Compaq Computer Corporation Reducing power consumption in computer memory
EP1530218A2 (en) * 2003-11-05 2005-05-11 Fujitsu Limited Semiconductor integrated circuit having temperature detector

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101640065B (en) * 2008-07-29 2012-07-04 国际商业机器公司 Refresh controller and refresh control method used for embedded DRAM
US11837272B2 (en) 2018-08-03 2023-12-05 Lodestar Licensing Group Llc Methods for row hammer mitigation and memory devices and systems employing the same
US11810610B2 (en) 2018-10-09 2023-11-07 Lodestar Licensing Group Llc Methods for row hammer mitigation and memory devices and systems employing the same
WO2020131457A1 (en) * 2018-12-21 2020-06-25 Micron Technology, Inc. Methods for activity-based memory maintenance operations and memory devices and systems employing the same
US11550650B2 (en) 2018-12-21 2023-01-10 Micron Technology, Inc. Methods for activity-based memory maintenance operations and memory devices and systems employing the same
US11947412B2 (en) 2018-12-21 2024-04-02 Lodestar Licensing Group Llc Methods for activity-based memory maintenance operations and memory devices and systems employing the same
US11604694B2 (en) 2018-12-31 2023-03-14 Micron Technology, Inc. Error correction in row hammer mitigation and target row refresh

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US8559259B2 (en) 2013-10-15
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US20090225617A1 (en) 2009-09-10
US8902688B2 (en) 2014-12-02
US20120155201A1 (en) 2012-06-21
KR20080012384A (en) 2008-02-11
US20060268643A1 (en) 2006-11-30
TW200641891A (en) 2006-12-01
US7532532B2 (en) 2009-05-12
JP2008542967A (en) 2008-11-27
US8130585B2 (en) 2012-03-06
CN101189680A (en) 2008-05-28

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