WO2015147016A1 - 抵抗変化型記憶素子のデータ書き込み装置 - Google Patents
抵抗変化型記憶素子のデータ書き込み装置 Download PDFInfo
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- WO2015147016A1 WO2015147016A1 PCT/JP2015/058988 JP2015058988W WO2015147016A1 WO 2015147016 A1 WO2015147016 A1 WO 2015147016A1 JP 2015058988 W JP2015058988 W JP 2015058988W WO 2015147016 A1 WO2015147016 A1 WO 2015147016A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0064—Verifying circuits or methods
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- 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
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1675—Writing or programming circuits or methods
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- 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
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1677—Verifying circuits or methods
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
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- 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
- G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
- G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
- G11C11/165—Auxiliary circuits
- G11C11/1653—Address circuits or decoders
- G11C11/1657—Word-line or row circuits
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0004—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising amorphous/crystalline phase transition cells
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0007—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements comprising metal oxide memory material, e.g. perovskites
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0064—Verifying circuits or methods
- G11C2013/0066—Verify correct writing whilst writing is in progress, e.g. by detecting onset or cessation of current flow in cell and using the detector output to terminate writing
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
- G11C2013/0073—Write using bi-directional cell biasing
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
- G11C2013/0078—Write using current through the cell
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C13/00—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00
- G11C13/0002—Digital stores characterised by the use of storage elements not covered by groups G11C11/00, G11C23/00, or G11C25/00 using resistive RAM [RRAM] elements
- G11C13/0021—Auxiliary circuits
- G11C13/0069—Writing or programming circuits or methods
- G11C2013/0083—Write to perform initialising, forming process, electro forming or conditioning
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/10—Input/output [I/O] data interface arrangements, e.g. I/O data control circuits, I/O data buffers
- G11C7/1078—Data input circuits, e.g. write amplifiers, data input buffers, data input registers, data input level conversion circuits
- G11C7/1096—Write circuits, e.g. I/O line write drivers
Definitions
- the present invention relates to a resistance variable memory element data writing device.
- a resistance change type memory element such as an MTJ (Magnetic Tunneling Junction) element changes its resistance state when a write current is supplied.
- MTJ Magnetic Tunneling Junction
- a sufficient time for changing the resistance state of the memory element is secured for supplying the write current to the resistance change type memory element.
- this method consumes wasted power because the write current continues to be supplied to the memory element even after the resistance state of the resistance change type memory element changes (even after data is completely written).
- Non-Patent Documents 1 to 4 disclose techniques for detecting the end of data writing to a resistance change type storage element.
- Non-Patent Documents 1 to 3 disclose devices that intermittently read data stored in a storage element and detect the end of writing when data to be written is read.
- Non-Patent Document 4 discloses an apparatus for detecting the end of data writing when the voltage at one end of the resistance change type storage element changes to a voltage corresponding to data to be written.
- Non-Patent Documents 1 to 3 if the interval for reading data from the storage element is long, there is a time difference from the actual end of data writing until the end of data writing is detected. There is a problem of consuming wasteful power by the amount. On the other hand, if the interval for reading data from the storage element is short, there is a problem that the number of times data is read increases and the power consumption increases.
- the device disclosed in Non-Patent Document 4 may have a large or small change in the detected voltage depending on the direction of the write current flowing through the memory element. If the change in the detected voltage is small, the end of data writing may not be detected correctly. For this reason, the apparatus disclosed in Non-Patent Document 4 has a problem that the detection margin for the end of writing is low. Further, the device disclosed in Non-Patent Document 4 needs to include a circuit that detects a change in voltage at one end of the storage element for each data to be written, and this circuit includes a flip-flop with a reset function and the like. Therefore, there is a problem that the circuit area is large.
- the present invention has been made in view of such circumstances, and an object of the present invention is to provide a data writing apparatus that has a high detection margin for writing completion and reduces power consumption during data writing by a simple circuit configuration. To do.
- a resistance variable memory element data writing device of the present invention comprises: A drain terminal of the first NMOS transistor is connected to a drain terminal of the first PMOS transistor, and a first connection node connecting the drain terminal of the first PMOS transistor and the drain terminal of the first NMOS transistor, One end of the resistance change type storage element is connected, The drain end of the second PMOS transistor is connected to the drain end of the second NMOS transistor, and the second connection node connecting the drain end of the second PMOS transistor and the drain end of the second PMOS transistor is connected to the second connection node.
- Writing means for passing current through the current path and writing data to the memory element; After starting the writing of data to the storage element, the voltage of the first connection node or the second connection node is monitored according to the data to be written, and the data of the data is based on the voltage at one end.
- Write end detection means for detecting the end of writing and supplying a write end signal indicating the end of writing of the data;
- Write control means for stopping writing of the data to the storage element by the writing means in response to the write end signal supplied by the writing end detection means.
- the write end detection means supplies the write end signal when, for example, the voltage at one end of the storage element exceeds a preset threshold value or falls below a threshold value.
- the write end detection means includes, for example, an inverter, and the inverter outputs the write end signal when the voltage at one end of the storage element exceeds or falls below a threshold set in the inverter. To do.
- the write end detection means When the voltage at the end of 1 changes from a value smaller than a first threshold value to a larger value, and the second data is written to the memory element by the writing means, and the memory element has a high resistance state When the voltage at the second end of the memory element changes from a value greater than a second threshold value to a smaller value due to a change from low to low, the write end signal is output.
- the write end detection means includes means for selecting one of the voltage at the first end and the voltage at the second end of the write means according to the data to be written, for example.
- the write control means includes, for example, a write request reception unit that receives a request for writing first data or second data, and the storage according to the write request for the first data received by the write request reception unit.
- a first write control unit for causing the writing means to execute the writing of the first data to an element; and the second data writing request received by the write request receiving unit, according to the request for writing the second data.
- a second write control unit that causes the write unit to write second data, and the first write control unit corresponds to the first data supplied from the write end detection unit.
- the writing unit stops writing the first data to the storage element, and
- the write control unit of 2 stops writing of the second data to the storage element by the write unit in response to a write end signal corresponding to the second data supplied from the write end detection unit
- a plurality of the storage elements are arranged, and end portions of the storage elements are connected to a pair of bit lines via a selection transistor, and the writing unit is connected to the pair of bit lines.
- the data to be written is written to the selected storage element, and the write end detection means finishes writing the data based on the voltage of one bit line to which one end of the selected storage element is connected Detect that
- FIG. 1 is a block diagram of a data writing device according to an embodiment of the present invention.
- (A) is the figure which showed the structure of the MTJ element of a high resistance state.
- (B) is a diagram showing a configuration of an MTJ element in a low resistance state.
- FIG. 2 is a diagram illustrating a circuit configuration of a write control unit illustrated in FIG. 1.
- FIG. 2 is a diagram illustrating a circuit configuration of a write drive unit and a write end detection unit illustrated in FIG. 1.
- A) is the timing chart which showed the time change of the resistance value of an MTJ element.
- (B) is a timing chart showing temporal changes in the voltage of the bit line.
- (C) is a timing chart showing temporal changes in the voltage of the bit line bar.
- FIG. 10 is a diagram illustrating an operation of a write control unit when write data “0” is written.
- FIG. 5 is a diagram illustrating operations of a write driver and a write end detector when writing write data “0”.
- FIG. 6 is a diagram illustrating an operation of a write control unit when write data “0” is written.
- FIG. 6 is a diagram illustrating an operation of a write control unit when writing write data “1”.
- FIG. 10 is a diagram illustrating operations of a write driver and a write end detector when writing write data “1”.
- FIG. 6 is a diagram illustrating an operation of a write control unit when write data “1” is written. It is the block diagram which showed the structure of the data writing device which concerns on the 1st modification of this invention. It is the block diagram which showed the structure of the data writer which concerns on the 2nd modification of this invention.
- the data writing device 1 writes data to the memory cell MC.
- the memory cell MC has one MTJ (Magnetic Tunneling Junction) element M.
- the data writing device 1 writes data by causing a current corresponding to data “0” or “1” to be written to flow through the MTJ element M.
- the data writing device 1 detects the end of data writing and stops energization of the MTJ element M.
- write data D data to be written
- a current for writing data to the MTJ element M is referred to as a write current I.
- the data writing device 1 includes a write control unit 10, a write drive unit 20, and a write end detection unit 30.
- the write control unit 10 receives, for example, a signal representing the write data D and an enable bar signal / EN from an arithmetic processing circuit 100 of a CPU (Central Processing Unit). Further, the write control unit 10 receives a write end signal DONE from the write end detection unit 30. The write control unit 10 determines an effective write drive signal WR () according to the signal level of the enable bar signal / EN received from the arithmetic processing circuit 100 and the signal level of the write end signal DONE received from the write end detection unit 30. An active level write drive signal WR) or an invalid write drive signal WR (inactive level write drive signal WR) is supplied to the write drive unit 20.
- a signal representing the write data D and an enable bar signal / EN from an arithmetic processing circuit 100 of a CPU (Central Processing Unit). Further, the write control unit 10 receives a write end signal DONE from the write end detection unit 30. The write control unit 10 determines an effective write drive signal WR () according to the signal level of the enable bar signal
- the write control unit 10 After receiving the low level enable bar signal / EN, the write control unit 10 sends the active level write drive signal WR to the write drive unit 20 until the high level write end signal DONE is received. Supply. Further, the write control unit 10 supplies the write drive unit 20 with the write drive signal WR having the inactive level while receiving the high level enable bar signal / EN and the high level write end signal DONE.
- the write driver 20 is connected to the bit line BL and the bit line bar / BL.
- the write driver 20 receives an active level write drive signal WR from the write controller 10
- the write driver 20 supplies a write current I in a direction corresponding to the write data D to the bit line BL and the bit line bar / BL.
- the write current I flows through the current path formed from the bit line BL, the MTJ element M, and the bit line bar / BL, and the write data D “0” or “1” is written into the MTJ element M.
- the MTJ element M is composed of three layers: a pin (fixed) layer MP, an insulating layer MI, and a free (movable) layer MF.
- the pinned layer MP and the free layer MF are made of a material such as a ferromagnetic material (for example, CoFeB) or a ferromagnetic Heusler alloy (for example, Co2FeAl, Co2MnSi).
- the magnetization direction of the pinned layer MP is fixed, and the magnetization direction does not change even when a current flows through the layer.
- the magnetization direction of the free layer MF is variable, and when the current flows in the layer, the magnetization direction changes.
- the insulating layer MI is a thin film provided between the pinned layer MP and the free layer MF.
- the insulating layer MI is made of a material such as magnesium oxide (MgO), alumina (Al2O3), spinel single crystal (MgAl2O4), for example.
- FIG. 2B shows a state (parallel state) in which the magnetization directions of the pinned layer MP and the free layer MF are aligned with each other.
- FIG. 2A shows a state where the magnetization directions of the pinned layer MP and the free layer MF are not aligned (anti-parallel state).
- the resistance value of the MTJ element M is smaller in the parallel state than in the antiparallel state.
- the resistance state of the MTJ element M in the parallel state is referred to as a low resistance state, and the resistance state of the MTJ element M in the antiparallel state is referred to as a high resistance state.
- a write current I having a current value (current threshold) necessary for magnetization reversal is passed through the MTJ element M.
- current threshold a current value necessary for magnetization reversal
- the MTJ element M when the MTJ element M is in a low resistance state, when a write current I that is equal to or greater than the current threshold value flows from the pinned layer MP to the free layer MF, the magnetization direction of the free layer MF is reversed, and The direction of magnetization changes to the opposite direction. That is, the resistance state of the MTJ element M is switched to the high resistance state.
- the low resistance state of the MTJ element M is associated with data “0”, and the high resistance state is associated with data “1”. That is, the memory cell MC stores 1-bit data.
- the MTJ element M changes from the high resistance state to the low resistance state, data “0” is written in the memory cell MC.
- the MTJ element M changes from the low resistance state to the high resistance state, data “1” is written in the memory cell MC.
- the write end detection unit 30 is connected to a pair of bit lines BL and a bit line bar / BL.
- One end of the MTJ element M is connected to the bit line BL at a node SN0.
- the other end of the MTJ element M is connected to the bit line bar / BL at the node SN1.
- the write end detection unit 30 continuously monitors the voltage of the connection node selected according to the write data among the nodes SN0 and SN1.
- the write end detection unit 30 detects the end of data writing when the voltage of the selected node among the nodes SN0 and SN1 satisfies the threshold condition.
- the write end detection unit 30 has completed the data writing. Is detected.
- the threshold values of the nodes SN0 and SN1 are set to voltages V th0 and V th1 .
- the voltage V 0 at the connection node SN 0 and the voltage V 1 at the connection node SN 1 represent the voltage at one end of the MTJ element M, respectively.
- the write completion detecting section 30, the voltage V 1 of the node SN1 is exceeds the threshold value V th1, detecting the end of writing of the write data D "1".
- the write end detection unit 30 When the write end detection unit 30 detects the end of writing of the write data D, the write end detection unit 30 supplies the write control unit 10 with a high-level write end signal DONE indicating the end of writing.
- the write end detection unit 30 stops the supply of the high-level write end signal 10 when detecting that the writing of the next data is started by a signal representing the data D supplied from the arithmetic processing circuit 100.
- the write end detection unit 30 when the voltage V 0 which nodes SN0 is greater than the threshold V th0, or, when the voltage V 1 of the node SN1 is below the threshold value V th1 is a low level of the write end signal DONE is supplied to the write controller 10.
- the write control unit 10 includes a control signal supply unit 11 and a drive signal supply unit 12.
- the control signal supply unit 11 has a high level indicating whether or not data can be written according to the enable bar signal / EN supplied from the arithmetic processing circuit 100 and the write end signal DONE supplied from the write end detection unit 30.
- a low level write control signal WC is supplied to the drive signal supply unit 12.
- the control signal supply unit 11 includes a P-channel MOSFET (Metal Oxide Semiconductor Field-effect transistor) 111 and N-channel MOSFETs 112 and 113.
- MOSFET Metal Oxide Semiconductor Field-effect transistor
- the source of the P-channel MOSFET 111 is connected to the power supply via the power supply line VDD, the drain is connected to the drain of the N-channel MOSFET 112, and the gate is connected to the arithmetic processing circuit 100 via the signal line.
- the enable bar signal / EN is input from the arithmetic processing circuit 100 to the gate.
- the drain of the N-channel MOSFET 112 is connected to the drain of the P-channel MOSFET 111, the source is connected to the drain of the N-channel MOSFET 113, and the gate is connected to the write end detection unit 30 via a signal line.
- a write end signal DONE is input from the write end detector 30 to the gate.
- the drain is connected to the source of the N-channel MOSFET 112, the source is connected to the ground line GND, and the gate is connected to the arithmetic processing circuit via the signal line.
- the enable bar signal / EN is input from the arithmetic processing circuit 100 to the gate.
- the node 114 is a connection point between the P-channel MOSFET 111 and the N-channel MOSFET 112.
- the node 114 is connected to the inverter 121 of the drive signal supply unit 12 through a signal line.
- a high-level or low-level write control signal WC corresponding to the potential of the node 114 is supplied to the drive signal supply unit 12.
- the low-level enable bar signal / EN is a signal for starting data writing to the MTJ element M.
- the write end detection unit 30 when the write end detection unit 30 outputs a high level write end signal DONE, the N-channel MOSFET 112 is turned on.
- the write end detection unit 30 outputs a high-level write end signal DONE after detecting the end of data writing until it detects the start of writing of data different from the data. Specifically, the write end detection unit 30 detects the start of the writing of the data “0” after detecting the end of the writing of the data “0” and the writing of the data “1”.
- a high-level write end signal DONE is output after the end is detected until the start of writing of data “0” is detected.
- an initialization state a state in which the P-channel MOSFET 111 and the N-channel MOSFET 112 are on and the N-channel MOSFET 113 is off is referred to as an initialization state.
- charges are stored in a region (node 114) between the P-channel MOSFET 111 and the N-channel MOSFET 113 by the power supply voltage applied via the power supply line VDD.
- a high-level write control signal WC is supplied to the drive signal supply unit 12 by the electric charge stored in the node 114.
- the write end detection unit 30 When the write end detection unit 30 outputs a low-level write end signal DONE, the N-channel MOSFET 112 is turned off.
- the low-level write end signal DONE is supplied from the write end detector 30 from the start of writing of the write data D until the resistance state of the MTJ element M changes.
- a region (node 114) between the P-channel MOSFET 111 and the N-channel MOSFET 112 is applied by the power supply voltage applied through the power supply line VDD. Charge is stored.
- a high-level write control signal WC is supplied to the drive signal supply unit 12 by the electric charge stored in the node 114.
- the arithmetic processing circuit 100 When the arithmetic processing circuit 100 outputs a high level enable bar signal / EN, the P-channel MOSFET 111 is turned off and the N-channel MOSFET 113 is turned on. In this state, the write control signal supply unit 11 waits for the high level write end signal DONE to be supplied from the write end detection unit 30, and immediately receives the MTJ when the high level write end signal DONE is supplied. Prepare to stop writing to element M.
- the arithmetic processing circuit 100 has a high level for a predetermined period (a time sufficiently shorter than the time until the resistance state of the MTJ element M changes, for example, several nanoseconds) after the output of the low level enable bar signal / EN is started. The output of the enable bar signal / EN is continued.
- the arithmetic processing circuit 100 stops outputting the low level enable bar signal / EN and starts outputting the high level enable bar signal / EN.
- the low-level enable bar signal / EN is output during a period from time t1 to time t1 'and from time t4 to time t4'.
- a high-level write control signal WC is supplied to the drive signal supply unit 12 by the charge stored in the node 114.
- the low-level write control signal WC is supplied to the drive signal supply unit 12.
- the drive signal supply unit 12 outputs a write drive signal WR corresponding to the signal representing the write data D supplied from the arithmetic processing circuit 100 and the write control signal WC supplied from the control signal supply unit 11. Output to.
- the drive signal supply unit 12 outputs a valid write drive signal WR to the write drive unit 20 while the high level write control signal WC is supplied. Specifically, according to the write data D, the drive signal supply unit 12 sets one of the write drive signals WR0 and / WR0 or the write drive signals WR1 and / WR1 as an active level and sets the other as an inactive level. To do.
- the drive signal supply unit 12 outputs the inactive level write drive signal WR regardless of whether the write data D is “0” or “1”. The data is output to the writing drive unit 20.
- the drive signal supply unit 12 includes inverters 121, 122, 125, 126 and NOR gates 123, 124.
- the drive signal supply unit 12 uses the inverters 121, 122, and 125 and the NOR gate 123 to drive the high level write drive.
- the signal WR1 and the low level write drive signal / WR1 are supplied to the write drive unit 20. Note that the write drive signal WR0 is at a low level, and the write drive signal / WR0 is at a high level.
- the drive signal supply unit 12 uses the inverters 121 and 126 and the NOR gate 124 to perform high-level write drive.
- the signal WR0 and the low-level write drive signal / WR0 are supplied to the write drive unit 20. Note that the write drive signal WR1 is at a low level and the write drive signal / WR1 is at a high level.
- the write drive unit 20 includes a bit line drive unit 21 and a bit line bar drive unit 22.
- the bit line driving unit 21 is connected to the bit line BL.
- the bit line bar driving unit 22 is connected to the bit line bar / BL.
- the bit line driving unit 21 and the bit line bar driving unit 22 are connected to the writing control unit 10 by signal lines.
- the bit line drive unit 21 and the bit line bar drive unit 22 cause the write current I to flow through the MTJ element M based on the signal level of the write drive signal WR supplied from the write control unit 10.
- the bit line driving unit 21 includes a P-channel MOSFET 211 and an N-channel MOSFET 212.
- the source of the P-channel MOSFET 211 is connected to the power supply via the power supply line VDD, the drain is connected to the bit line BL, and the gate is connected to the write control unit 10 via the signal line.
- a write drive signal / WR0 is input from the write controller 10 to the gate.
- the source is connected to the ground line GND, the drain is connected to the bit line BL, and the gate is connected to the write control unit 10 via the signal line.
- a write drive signal WR1 is input from the write controller 10 to the gate.
- the bit line bar driving unit 22 includes an N-channel MOSFET 221 and a P-channel MOSFET 222.
- the source is connected to the ground line GND, the drain is connected to the bit line bar / BL, and the gate is connected to the write control unit 10 via the signal line.
- a write drive signal WR0 is input from the write control unit 10 to the gate.
- the source of the P-channel MOSFET 222 is connected to the power supply via the power supply line VDD, the drain is connected to the bit line bar / BL, and the gate is connected to the drawing control unit 10 via the signal line.
- a write drive signal / WR1 is input from the write controller 10 to the gate.
- the write control unit 10 When the write control unit 10 outputs the low level write drive signal / WR0 and the high level write drive signal WR0, the P-channel MOSFET 211 and the N-channel MOSFET 221 are turned on. As a result, the write current I (forward current) flows from the power supply line VDD in the order of the P channel MOSFET 211, the bit line BL, the MTJ element M, the bit line bar / BL, the N channel MOSFET 221, and the ground line GND. In this way, the write data D “0” is written to the MTJ element M.
- the write control unit 10 when the write control unit 10 outputs the high level write drive signal WR1 and the low level write drive signal / WR1, the N-channel MOSFET 212 and the P-channel MOSFET 222 are turned on. As a result, the write current I (reverse current) flows from the power supply line VDD in the order of the P channel MOSFET 222, the bit line bar / BL, the MTJ element M, the bit line BL, the N channel MOSFET 212, and the ground line GND. In this way, the write data D “1” is written to the MTJ element M.
- the write control unit 10 When the write control unit 10 outputs a high-level write drive signal / WR0, a low-level write drive signal WR0, a low-level write drive signal WR1, and a high-level write drive signal / WR1, the P-channel MOSFET 211 and the N-channel MOSFET 221, N The channel MOSFET 212 and the P channel MOSFET 222 are turned off. In this case, the write current I does not flow through the MTJ element M.
- the write end detection unit 30 selects either the node SN0 or SN1 according to the write data D, and detects the end of data writing based on the voltage of the selected node. Then, the write end detection unit 30 outputs a write end signal DONE to the write control unit 10.
- the write end detection unit 30 includes inverters 31, 32, 33, 34, a multiplexer 35, and an XNOR gate 36.
- the inverters 31 and 32 and the inverters 33 and 34 each function as a buffer.
- a write current I for writing “0” to the MTJ element was supplied from time t1 to time t2.
- the write current I equal to or higher than the current threshold flows through the MTJ element M
- the resistance state of the MTJ element changes, and the resistance value of the MTJ element M decreases at time t2, as shown in FIG. . That is, the writing of “0” to the MTJ element M is completed.
- the voltage V 0 at the node SN0 is greater than the voltage V 1 at the node SN1.
- a write current I for writing “1” to the MTJ element was supplied from time t 4 to time t 5.
- the resistance value of the MTJ element M increases at time t5. That is, the writing of “1” to the MTJ element M is completed.
- the voltage V 1 at the node SN1 and the voltage V 0 at the node SN0 increase when the MTJ element M changes from the low resistance state to the high resistance state at time t5.
- the degree of change of the voltage at this time is, towards the voltage V 1 of the node SN1 is greater than the voltage V 0 which node SN 0.
- the minimum value of the voltage V 0 when the MTJ element M changes from the high resistance state to the low resistance state is larger than the maximum value of the voltage V 0 when the MTJ element M changes from the low resistance state to the high resistance state. large.
- the minimum value of the voltage V 1 when the MTJ element M changes from the low resistance state to the high resistance state is larger than the maximum value of the voltage V 1 when the MTJ element M changes from the high resistance state to the low resistance state. large.
- the inverter 31 is set with a threshold value V th0 for detecting the end of writing of the write data “0”.
- the inverter 33 is set with a threshold value V th1 for detecting the end of writing of the write data “1”.
- the inverter 31 when the inverter 31 is composed of a CMOS (Complementary MOS), the size (gate width, gate length) of the P-channel MOSFET 31a and the N-channel MOSFET 31b, or the P-channel MOSFET 31a and N
- CMOS Complementary MOS
- the concentration of the impurity added to the channel MOSFET 31b a threshold V th0 as shown in the following equation is set in the inverter 31.
- V 0p ⁇ V th0 ⁇ V 0ap V 0ap Voltage of the node SN0 when the MTJ element M is in the high resistance state
- V 0p Voltage of the node SN0 when the MTJ element M is in the low resistance state
- the inverter 33 has a threshold value V th1 as shown in the following equation: Is set.
- V 1p ⁇ V th1 ⁇ V 1ap V 1ap Voltage of the node SN1 when the MTJ element M is in the high resistance state
- V 1p Voltage of the node SN1 when the MTJ element M is in the low resistance state
- V th1 (V 1ap + V 1p ) / 2
- the multiplexer 35 receives output signals from the inverters 32 and 34 and a signal representing the write data D supplied from the arithmetic processing circuit 100.
- the multiplexer 35 selects a signal corresponding to the write data D from the output signals of the inverter 32 and the inverter 34 and supplies the selected signal to the XNOR gate 36. For example, when the write data D is “0”, the multiplexer 35 supplies the output signal of the inverter 32 to the XNOR gate 36. When the write data D is “1”, the multiplexer 35 supplies the output signal of the inverter 34 to the XNOR gate 36.
- the XNOR gate 36 outputs XNOR (Negative Exclusive OR) having the signal representing the write data D supplied from the arithmetic processing circuit 100 and the output signal of the multiplexer 35 as inputs as a write end signal DONE.
- XNOR Negative Exclusive OR
- the multiplexer 35 When the write data D is “0” (the signal level is low level) and the voltage V 0 of the node SN0 exceeds the threshold value V th0 , the multiplexer 35 outputs a high level signal. In this case, the XNOR gate 36 outputs a low-level write end signal DONE.
- the multiplexer 35 When the write data D is “0” (signal level is low level) and the voltage V 0 of the node SN0 is lower than the threshold value V th0 , the multiplexer 35 outputs a low level signal. In this case, the XNOR gate 36 outputs a high-level write end signal DONE.
- the write data D is "1" (signal level a high level)
- the voltage V 1 of the node SN1 is below the threshold value V th1
- the multiplexer 35 outputs a low level signal.
- the XNOR gate 36 outputs a low-level write end signal DONE.
- the write data D is "1" (signal level a high level)
- the voltage V 1 of the node SN1 exceeds the threshold value V th1
- the multiplexer 35 outputs a high level signal.
- the XNOR gate 36 outputs a high-level write end signal DONE. In this way, the write end signal DONE output from the write end detection unit 30 is supplied to the write control unit 10.
- the data writing device 1 configured as described above writes data “0” or “1” to the MTJ element M based on the write data D and the enable bar signal / EN received from the arithmetic processing circuit 100.
- the arithmetic processing circuit 100 outputs a low level enable bar signal / EN for a predetermined period (data write request).
- the P-channel MOSFET 111 of the control signal supply unit 11 is turned on and the N-channel MOSFET 113 is turned off by the low level enable bar signal / EN.
- the write end detection unit 30 outputs a high level write end signal DONE after detecting the end of writing of the previous data. For this reason, the N-channel MOSFET 112 is kept on. That is, when the low level enable bar signal / EN is supplied from the arithmetic processing circuit 100, the initialization state (P-channel MOSFET 111 and N-channel MOSFET 112 are on, N-channel MOSFET 113 is off).
- a signal (low level) representing the write data “0” supplied from the arithmetic processing circuit 100 is input to the drive signal supply unit 12.
- the drive signal supply unit 12 receives the high-level write drive signal WR0 and the low-level write drive signal / WR0 (active level write).
- the drive signal WR) is supplied to the write driver 20. Note that the write drive signal WR1 is at a low level and the write drive signal / WR1 is at a high level.
- the P-channel MOSFET 211 of the bit line driving unit 21 and the N-channel MOSFET 221 of the bit line bar driving unit 22 are turned on. That is, the write current I (forward current) flows through the current path formed by the power supply line VDD, the P-channel MOSFET 211, the bit line BL, the MTJ element M, the bit line bar / BL, and the N-channel MOSFET 221 indicated by the broken line arrows.
- the XNOR gate 36 receives a signal (low level) representing the write data D “0” supplied from the arithmetic processing circuit 100 and a high level signal supplied from the multiplexer 35.
- a low level write end signal DONE is output. That is, when writing of the write data “0” is started to the MTJ element M in the high resistance state (data “1” is stored), the write end detection unit 30 ends the low-level write to the write control unit 10. Supply of the signal DONE is started. As shown in FIGS. 5D and 5E, immediately after the enable bar signal / EN becomes low level and writing of the write data starts, the write end signal DONE becomes low level.
- the N-channel MOSFET 112 of the control signal supply unit 11 is turned off.
- the P-channel MOSFET 111 is kept on and the N-channel MOSFET 113 is kept off.
- the high level write control signal WC continues to be supplied to the drive signal supply unit 12 by the electric charge stored in the node 114.
- the drive signal supply unit 12 supplies the write drive unit 20 with the high level write drive signal WR0, the low level write drive signal / WR0, the low level write drive signal WR1, and the high level write drive signal / WR1. . That is, even when the write control unit 10 receives the low-level write end signal DONE from the write end detection unit 30, the write control unit 10 continues to supply the write drive unit 20 with the active level write drive signal WR.
- the arithmetic processing circuit 100 stops supplying the low-level enable bar signal / EN when a predetermined period elapses after the supply of the low-level enable bar signal / EN is started. Then, the arithmetic processing circuit 100 starts to supply a high level enable bar signal. By supplying the high level enable bar signal / EN, the P-channel MOSFET 111 is turned off and the N-channel MOSFET 113 is turned on. On the other hand, the N-channel MOSFET 112 remains off. Also at this time, the high level write control signal WC continues to be supplied to the drive signal supply unit 12 by the electric charge stored in the node 114.
- the drive signal supply unit 12 supplies the write drive unit 20 with the high level write drive signal WR0, the low level write drive signal / WR0, the low level write drive signal WR1, and the high level write drive signal / WR1. That is, even when the write control unit 10 receives the high level enable bar signal / EN from the arithmetic processing circuit 100, the write control unit 10 continues to supply the write drive unit 20 with the active level write drive signal WR.
- the MTJ element M is shown in FIG. Switch to a low resistance state.
- the voltage V 0 which nodes SN0 is smaller than the threshold V th0 of the inverter 31.
- the XNOR gate 36 receives a signal (low level) representing the write data D “0” supplied from the arithmetic processing circuit 100 and a low level signal supplied from the multiplexer 35. Therefore, the XNOR gate 36 outputs a high level write end signal DONE. That is, when the MTJ element M changes from the high resistance state to the low resistance state, the write end detection unit 30 starts to supply the high level write end signal DONE to the write control unit 10.
- the N-channel MOSFET 112 is turned on.
- the P-channel MOSFET 111 is turned off and the N-channel MOSFET 112 and the N-channel MOSFET 113 are turned on, and the charge stored in the region (node 144) between the P-channel MOSFET 111 and the N-channel MOSFET 112 is discharged to the ground line GND.
- the write control signal WC supplied from the control signal supply unit 11 to the drive signal supply unit 12 is at a low level. Therefore, the write drive signal WR0 is at a low level and the write drive signal / WR0 is at a high level. That is, as shown in FIGS. 5E and 5F, when receiving the high-level write end signal DONE, the write control unit 10 causes the write drive unit 20 to stop supplying the write current I. Thus, the writing of the write data D “0” to the MTJ element M is completed.
- the arithmetic processing circuit 100 outputs a low-level enable bar signal / EN for a predetermined period (data write request). Therefore, the P-channel MOSFET 111 is turned on, the N-channel MOSFET 112 is turned on, and the N-channel MOSFET 113 is turned off (initialized state). Then, the high level write control signal WC is supplied to the drive signal supply unit 12 by the electric charge stored in the node 114.
- a signal (high level) representing the write data D “1” supplied from the arithmetic processing circuit 100 is input to the drive signal supply unit 12.
- the drive signal supply unit 12 supplies a high level write drive signal WR1 and a low level write drive signal / WR1 (active level write drive signal) by supplying a high level write control signal WC and a signal representing the write data D “1”.
- WR is supplied to the write driver 20.
- the drive signal WR0 is at a low level, and the write drive signal / WR0 is at a high level.
- the write current I (reverse current) flows in the order of the P-channel MOSFET 222, the bit line bar / BL, the MTJ element M, the bit line BL, and the N-channel MOSFET 212 from the power supply line VDD indicated by the broken line arrow shown in FIG.
- the voltage V 1 of the node SN1 at this time is smaller than the threshold value V th1 of the inverter 33.
- the XNOR gate 36 starts outputting the low-level write end signal DONE. That is, when writing of the write data “1” is started to the MTJ element M in the low resistance state (data “0” is stored), the write end detection unit 30 causes the write control unit 10 to end the low-level write. Output of the signal DONE is started.
- the write control unit 10 continues to supply the write drive unit 20 with the write drive signal WR having an active level.
- the arithmetic processing circuit 100 stops supplying the low-level enable bar signal / EN when a predetermined period elapses after the supply of the low-level enable bar signal / EN is started. Then, the arithmetic processing circuit 100 starts supplying the high-level enable bar signal / EN. By supplying the high level enable bar signal / EN, the P-channel MOSFET 111 is turned off and the N-channel MOSFET 113 is turned on. On the other hand, the N-channel MOSFET 112 maintains an off state. Also at this time, the write control unit 10 continues to supply the write drive unit 20 with the write drive signal WR having an active level.
- the MTJ element M When the write current I equal to or higher than the current threshold flows from the pinned layer MP of the MTJ element M in the low resistance state shown in FIG. 11 to the free layer MF, the MTJ element M is shown in FIG. Switch to the high resistance state.
- the voltage V 1 of the node SN1 is larger than the threshold value V th1 of the inverter 33.
- the XNOR gate 36 is supplied with a signal (high level) representing the write data D “1” supplied from the arithmetic processing circuit 100 and a high level signal supplied from the multiplexer 35. 36 outputs a high-level write end signal DONE. That is, when the MTJ element M changes from the low resistance state to the high resistance state, the write end detection unit 30 starts to supply a high level write end signal DONE to the write control unit 10.
- the N-channel MOSFET 112 When the high-level write end signal DONE is input to the gate of the N-channel MOSFET 112 of the write control unit 10, the N-channel MOSFET 112 is turned on. At this time, the P-channel MOSFET 111 is turned off and the N-channel MOSFET 112 and the N-channel MOSFET 113 are turned on, and the charge stored in the region (node 114) between the P-channel MOSFET 111 and the N-channel MOSFET 112 is discharged to the ground line GND.
- the write control unit 10 when receiving the high-level write end signal DONE, the write control unit 10 causes the write drive unit 20 to stop supplying the write current I. Thus, the writing of the write data D “1” to the MTJ element M is completed.
- the data writing device 1 continuously applies the voltage of any one of the nodes SN0 and SN1 of the bit line BL and the bit line bar / BL according to the write data D. To monitor. When the voltage of the monitored node satisfies the threshold condition, the data writing device 1 detects the end of writing of the data D to the MTJ element M. With this configuration, it is possible to reduce power consumption during data writing with a high write end detection margin and a simple circuit configuration.
- the write control unit 10 ends the data write when receiving the high-level enable bar signal / EN from the arithmetic processing circuit 100. .
- the write end detection unit 30 of the above embodiment includes two stages of four inverters 31, 32, 33, and 34, respectively.
- the write end detection unit 30 may include two buffers that detect that the voltages V 0 and V 1 of the nodes SN0 and SN1 satisfy the threshold condition.
- the write end detection unit 30 may include a plurality of stages of four or more inverters that detect that the voltages V 0 and V 1 of the nodes SN 0 and SN 1 satisfy the threshold condition.
- the write end detection unit 30 detects when the voltage V 0 of the node SN0 is lower than the threshold value V th0 or when the voltage V 1 of the node SN1 is higher than the threshold value V th1 (one of the nodes SN0 and SN1 is a threshold value). If the high-level write end signal DONE is output when the condition is satisfied and the low-level write end signal DONE is output otherwise, the circuit configuration of the write end detection unit 30 can be changed as appropriate. In this case, the inverters 31 to 34, the multiplexer 35, and the XNOR gate 36 may be appropriately omitted or changed to another configuration. In this case, the arithmetic processing circuit 100 may not supply the write data D to the write end detection unit 30.
- the memory cell MC may include a pair of MTJ elements M.
- the resistance states of the pair of MTJ elements M are set in a complementary manner, one being a high resistance state and the other being a low resistance state.
- a combination of resistance states of the pair of MTJ elements M is associated with data D “1” or “0”.
- the data writing device 1 monitors the voltage of any of the nodes SN0 and SN1 according to the write data D. When determining that the voltage of the node corresponding to the write data D satisfies the threshold condition, the data writing device 1 detects the end of data writing to the memory cell MC (a pair of MTJ elements M).
- the data writing device 1 When the memory circuit is composed of a plurality of memory cells, the data writing device 1 is provided with the word line driving unit 110 for selecting each memory cell MC, thereby completing the data writing for each memory cell MC. It can be detected.
- FIG. 14 shows a memory circuit having a plurality of memory cells MC.
- the plurality of memory cells MC are arranged in a matrix, and the write drive unit 20 and the write end detection unit 30 are arranged for each row.
- Each memory cell MC is connected to a word line WLC for individually selecting the memory cell MC and a word line WLS for selecting a plurality of memory cells MC for each section.
- the word line driving unit 110 receives information (coordinate values, etc.) indicating the position of the memory cell MC to be written from the arithmetic processing circuit 100.
- the word line driving unit 110 decodes information (coordinate values and the like) indicating the received position, and specifies the position (row and column) of the memory cell MC.
- the word line driver 110 outputs an active level signal to the word lines WLS and WLC connected to the memory cell MC based on the specified position of the memory cell MC.
- the word line driver 110 activates the word lines WLS and WLC connected to the write destination memory cell MC to make the memory cell MC writable. For example, when the position of the memory cell MC1 is specified, the word line driver 110 outputs an active level signal to the word line WLS and the word line WLC1 connected to the memory cell MC1, and the memory cell MC1 is writable.
- the write control unit 10 supplies an active level write drive signal to the write drive unit 20 corresponding to the specified row of the memory cells MC.
- the write driver 20 generates the write current in the direction corresponding to the write data based on the active level write drive signal received from the write controller 10, the bit line BL, the bit Supply to line bar / BL. As a result, a write current flows through the MTJ element M of the memory cell MC1, and write data is written into the MTJ element M.
- the write end detection unit 30 In the write end detection unit 30 arranged in the same row as the write drive unit 20, when the voltage of the connection node (node SN0) corresponding to the write data (for example, data “0”) exceeds the threshold (V th0 ) At this time, it is detected that data writing has been completed, and a high-level write end signal DONE is supplied to the write control unit 10. When the high-level write end signal DONE is supplied from the write end detection unit 30, the write control unit 10 causes the write drive unit 20 to stop supplying the write current. Thereby, the data writing to the MTJ element M of the memory cell MC1 is completed.
- the storage element for writing the write data is not limited to the MTJ element, and may be a resistance change type storage element such as ReRAM (Resistance Random Access Memory).
- the present invention is based on Japanese Patent Application No. 2014-60901 filed on March 24, 2014.
- the specification, claims and drawings of Japanese Patent Application No. 2014-60901 are incorporated in the present invention as a reference.
- the present invention it is possible to reduce the power consumption at the time of data writing with a simple circuit configuration and a high write end detection margin for data writing to the resistance change type storage element.
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Abstract
Description
第1のPMOSトランジスタのドレイン端に第1のNMOSトランジスタのドレイン端が接続され、前記第1のPMOSトランジスタのドレイン端と前記第1のNMOSトランジスタのドレイン端とを接続する第1接続ノードに、抵抗変化型の記憶素子の一方の端が接続され、
第2のNMOSトランジスタのドレイン端に第2のPMOSトランジスタのドレイン端が接続され、前記第2のPMOSトランジスタのドレイン端と前記第2のPMOSトランジスタのドレイン端とを接続する第2接続ノードに前記記憶素子の他方の端が接続され、
書き込み対象のデータに応じ、前記第1のPMOSトランジスタと前記記憶素子と前記第2のNMOSトランジスタを含む電流路、または、前記第2のPMOSトランジスタと前記記憶素子と前記第1のNMOSトランジスタとを含む電流路に電流を流し、前記記憶素子にデータを書き込む書き込み手段と、
前記記憶素子へのデータの書き込みを開始してから、書き込み対象のデータに応じ、前記第1接続ノード、または、前記第2接続ノードの電圧を監視し、この一端の電圧を基に前記データの書き込みが終了したことを検出し、前記データの書き込みが終了したことを表す書き込み終了信号を供給する書き込み終了検出手段と、
前記書き込み終了検出手段によって供給された前記書き込み終了信号に応答して、前記書き込み手段による前記記憶素子への前記データの書き込みを停止させる書き込み制御手段と、を備える。
図1に示すように、データ書き込み装置1は、メモリセルMCにデータを書き込む。メモリセルMCは1つのMTJ(Magnetic Tunneling Junction:磁気トンネル接合)素子Mを有する。データ書き込み装置1は、書き込み対象のデータ「0」または「1」に対応する電流をMTJ素子Mに流すことによりデータを書き込む。データ書き込み装置1は、MTJ素子Mの抵抗状態が変化するとデータの書き込み終了を検出し、MTJ素子Mへの通電を停止する。以下、書き込み対象のデータを書き込みデータD、MTJ素子Mにデータを書き込むための電流を書き込み電流Iという。
ピン層MPとフリー層MFは強磁性体、(例えばCoFeB)、強磁性ホイスラー合金(例えばCo2FeAl、Co2MnSi)等の材料から構成される。ピン層MPの磁化の方向は固定されており、層内を電流が流れてもその磁化の方向は変わらない。一方、フリー層MFの磁化の方向は可変であり、層内を電流が流れると、その磁化の方向は変化する。
PチャネルMOSFET111がオン、NチャネルMOSFET112、NチャネルMOSFET113がオフの状態であるとき、電源線VDDを介して印加される電源電圧によってPチャネルMOSFET111とNチャネルMOSFET112との間の領域(ノード114)には電荷が蓄えられる。ノード114に蓄えられた電荷によってハイレベルの書き込み制御信号WCが駆動信号供給部12に供給される。
インバータ31、32と、インバータ33、34は、それぞれバッファとして機能する。
V0p<Vth0<V0ap
V0ap:MTJ素子Mが高抵抗状態のときのノードSN0の電圧
V0p:MTJ素子Mが低抵抗状態のときのノードSN0の電圧
インバータ33には、以下の式に示されるような閾値Vth1が設定される。
V1p<Vth1<V1ap
V1ap:MTJ素子Mが高抵抗状態のときのノードSN1の電圧
V1p:MTJ素子Mが低抵抗状態のときのノードSN1の電圧
具体的には、閾値Vth0、Vth1は、以下の式に示されるような値とする。
Vth0=(V0ap+V0p)/2
Vth1=(V1ap+V1p)/2
このようにして、書き込み終了検出部30から出力された書き込み終了信号DONEが、書き込み制御部10に供給される。
10 書き込み制御部
11 制御信号供給部
12 駆動信号供給部
111 PチャネルMOSFET
112,113 NチャネルMOSFET
114 ノード
121,122,125,126 インバータ
123,124 NORゲート
20 書き込み駆動部
21 ビットライン駆動部
22 ビットラインバー駆動部
211,222 PチャネルMOSFET
212,221 NチャネルMOSFET
30 書き込み終了検出部
31,32,33,34 インバータ
35 マルチプレクサ
36 XNORゲート
MC メモリセル
M MTJ素子
MF フリー層
MI 絶縁層
MP ピン層
BL ビットライン
/BL ビットラインバー
SN0,SN1 ノード
DONE 書き込み終了信号
WR,WR0,/WR0,WR1,/WR1 書き込み駆動信号
D 書き込みデータ
/EN イネーブルバー信号
WC 書き込み制御信号
I 書き込み電流
Claims (7)
- 第1のPMOSトランジスタのドレイン端に第1のNMOSトランジスタのドレイン端が接続され、前記第1のPMOSトランジスタのドレイン端と前記第1のNMOSトランジスタのドレイン端とを接続する第1接続ノードに、抵抗変化型の記憶素子の一方の端が接続され、
第2のNMOSトランジスタのドレイン端に第2のPMOSトランジスタのドレイン端が接続され、前記第2のPMOSトランジスタのドレイン端と前記第2のPMOSトランジスタのドレイン端とを接続する第2接続ノードに前記記憶素子の他方の端が接続され、
書き込み対象のデータに応じ、前記第1のPMOSトランジスタと前記記憶素子と前記第2のNMOSトランジスタを含む電流路、または、前記第2のPMOSトランジスタと前記記憶素子と前記第1のNMOSトランジスタとを含む電流路に電流を流し、前記記憶素子にデータを書き込む書き込み手段と、
前記記憶素子へのデータの書き込みを開始してから、書き込み対象のデータに応じ、前記第1接続ノード、または、前記第2接続ノードの電圧を監視し、この一端の電圧を基に前記データの書き込みが終了したことを検出し、前記データの書き込みが終了したことを表す書き込み終了信号を供給する書き込み終了検出手段と、
前記書き込み終了検出手段によって供給された前記書き込み終了信号に応答して、前記書き込み手段による前記記憶素子への前記データの書き込みを停止させる書き込み制御手段と、を備える、
ことを特徴とする抵抗変化型記憶素子のデータ書き込み装置。 - 前記書き込み終了検出手段は、前記記憶素子の一端の電圧が予め設定された閾値を上回ったとき、あるいは下回ったときに前記書き込み終了信号を供給する、
ことを特徴とする請求項1に記載の抵抗変化型記憶素子のデータ書き込み装置。 - 前記書き込み終了検出手段は、インバータを備え、
前記インバータは、前記記憶素子の一端の電圧が前記インバータに設定された閾値を上回ったとき、あるいは下回ったときに前記書き込み終了信号を出力する、
ことを特徴とする請求項1または2に記載の抵抗変化型記憶素子のデータ書き込み装置。 - 前記書き込み終了検出手段は、
前記書き込み手段により、前記記憶素子に第1のデータが書き込まれて、前記記憶素子が、抵抗が低い状態から高い状態に変化したことにより、前記記憶素子の第1の端の電圧が第1の閾値より小さい値から大きい値に変化したとき、及び、
前記書き込み手段により、前記記憶素子に第2のデータが書き込まれて、前記記憶素子が、抵抗が高い状態から低い状態に変化したことにより、前記記憶素子の第2の端の電圧が第2の閾値より大きい値から小さい値に変化したとき、に前記書き込み終了信号を出力する、
ことを特徴とする請求項1、2または3に記載の抵抗変化型記憶素子のデータ書き込み装置。 - 前記書き込み終了検出手段は、
前記書き込み対象のデータに応じて、前記書き込み手段の第1の端の電圧と第2の端の電圧の一方を選択する手段を備える、
ことを特徴とする請求項1から4の何れか1項に記載の抵抗変化型記憶素子のデータ書き込み装置。 - 前記書き込み制御手段は、
第1のデータまたは第2のデータの書き込みの要求を受け付ける書き込み要求受付部と、
前記書き込み要求受付部が受け付けた前記第1のデータの書き込みの要求に従って、前記記憶素子への前記第1のデータの書き込みを前記書き込み手段に実行させる第1の書き込み制御部と、
前記書き込み要求受付部が受け付けた前記第2のデータの書き込みの要求に従って、前記記憶素子への前記第2のデータの書き込みを前記書き込み手段に実行させる第2の書き込み制御部と、を備え、
前記第1の書き込み制御部は、前記書き込み終了検出手段から供給された前記第1のデータに対応する書き込み終了信号に応答して、前記書き込み手段による前記記憶素子への前記第1のデータの書き込みを停止させ、
前記第2の書き込み制御部は、前記書き込み終了検出手段から供給された前記第2のデータに対応する書き込み終了信号に応答して、前記書き込み手段による前記記憶素子への前記第2のデータの書き込みを停止させる、
ことを特徴とする請求項1から5の何れか1項に記載の抵抗変化型記憶素子のデータ書き込み装置。 - 複数の前記記憶素子が配置され、
前記各記憶素子の端部は、選択用のトランジスタを介して一対のビットラインに接続されており、
前記書き込み手段は、前記一対のビットラインを介して選択された記憶素子に前記書き込み対象のデータを書き込み、
前記書き込み終了検出手段は、前記選択された記憶素子の一端が接続された一方の前記ビットラインの電圧に基づいて、前記データの書き込みが終了したことを検出する、
ことを特徴とする請求項1から6の何れか1項に記載の抵抗変化型記憶素子のデータ書き込み装置。
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WO2018100954A1 (ja) * | 2016-11-29 | 2018-06-07 | 国立大学法人東北大学 | 抵抗変化型記憶素子のデータ書き込み装置 |
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