JP2015099451A - Logical circuit with power saving function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently achieve power saving.SOLUTION: A power supply switching circuit 10 includes a power switch 12 that is provided between a power supply line VDDL and a circuit module 20, and that switches over between a first state (switch-ON) in which power is supplied from the power supply line VDDL to the circuit module 20 and a second state (switch-OFF) in which supply of power from the power supply line VDDL to the circuit module 20 is cut off. The power switch 12 switches over between the first state and the second state on the basis of a clock control signal CEN input from an outside for making a clock of the circuit module 20 valid or invalid. The circuit module 20 includes a nonvolatile storage circuit operating synchronously with a clock signal and retains a stored content even if the supply of power to the circuit module 20 stops.

Description

  The present invention relates to a logic circuit having a power saving function.

  In a semiconductor integrated circuit, a phenomenon called leakage current in which a current leaks to a place where an insulating layer should not flow by a few atoms is steadily generated due to progress of microfabrication technology. When leak current occurs frequently, wasteful power consumption increases. For this reason, it is necessary to suppress the leakage current in order to realize high integration of the circuit and low power consumption.

  As a technique for suppressing leakage current, power gating that stops power supply to a circuit is known. For example, Patent Document 1 discloses a power management unit that controls a power switch provided in each circuit module of a semiconductor integrated circuit. This power management unit determines whether or not each circuit module is used, and turns off the power switch of the circuit module that is determined not to be used to stop power feeding. According to this power management unit, power is supplied only to the circuit module that is determined to be in use, so that the occurrence of leakage current is suppressed and low power consumption can be achieved.

  On the other hand, as a technique for suppressing dynamic power due to charge / discharge of logic operation, a gated clock technique for stopping supply of an operation clock to an unused circuit module has been put into practical use. This is a technique for stopping useless charge / discharge current by stopping clock supply to a circuit module that does not need to operate by an enable signal for gating an operation clock (see Non-Patent Document 1, FIG. 2 and the like). .

  In the technique of Non-Patent Document 1, power is always supplied to the flip-flop. This is because if the supply of power to the flip-flop is stopped, the storage state of the flop-flop becomes indefinite when the power is supplied again, and the stored contents when the power supply is stopped cannot be reproduced. .

JP 2012-134321 A

Usami, K.; Ohkubo, N., Computer Design, 2006. ICCD 2006. International Conference on Digital Object Identifier: 10.1109 / ICCD.2006.4380809 Publication Year: 2006, Page (s): 155-161 "A Design Approach for Fine- grained Run-Time Power Gating using Locally Extracted Sleep Signals "

  In the power saving technique disclosed in Patent Document 1, the above power supply switching method may supply power to a circuit module even when the circuit module does not perform a substantial operation (does not function). In such a case, useless power is consumed by the leakage current of the circuit module in which no substantial operation is performed.

  Further, in the power saving method using the gated clock disclosed in Non-Patent Document 1, since power is always supplied to the flip-flop (memory element), power consumption of the flip-flop cannot be suppressed.

  An object of the present invention is to solve such a problem, and an object of the present invention is to provide a logic circuit that can achieve more efficient and low power consumption.

The logic circuit according to the present invention includes:
Based on a clock control signal for setting the clock signal to be valid or invalid, a clock signal output means for outputting the clock signal, a nonvolatile memory element that operates in response to the clock signal output from the clock signal output means, A circuit module comprising:
A first state that is provided between the power supply line and the circuit module, and that supplies power to the circuit module from the power supply line, and a second state that blocks supply of power from the power supply line to the circuit module. Switch means for setting based on the clock control signal,
It is characterized by that.

  For example, when the clock control signal for validly setting the clock signal of the circuit module is input, the switch means maintains the first state and invalidates the clock signal of the circuit module. When is input, the second state is maintained.

  And a logic operation circuit that performs a logic operation on the power control signal for instructing the supply and stop of power to the circuit module and the clock control signal, and the logic operation circuit is configured to supply power to the power control signal. And when the clock control signal effectively sets the clock signal of the circuit module, the switch means may be set to the first state.

  The circuit module performs a logical operation based on, for example, an input nonvolatile memory circuit that captures and outputs an input signal in response to the clock signal, and data stored in the input nonvolatile memory circuit A combinational circuit; and an output nonvolatile memory circuit that stores and outputs an output of the combinational circuit in response to the clock signal.

  According to the present invention, it is possible to achieve low power consumption more efficiently.

It is a figure which shows the structure of the semiconductor integrated circuit provided with the power supply switching circuit which concerns on one embodiment of this invention. It is the figure which showed the relationship between the signal level of the power supply control signal and clock control signal which are input into a logic gate, and the ON / OFF state of a power switch. It is a figure which shows the basic composition with which the circuit module shown in FIG. 1 is provided. (A) is a schematic diagram showing the amount of power consumption when switching between supply and cut-off of power to the circuit module based on the clock control signal, and (b) shows the supply of power to the circuit module based on the power control signal and It is a schematic diagram showing the power consumption when interruption | blocking is switched. It is a figure which shows the structure of the power supply switching circuit which concerns on the 1st modification of this invention. It is a figure which shows the structure of the power supply switching circuit which concerns on the 2nd modification of this invention. It is a figure which shows the structure of the power supply switching circuit which concerns on the 3rd modification of this invention.

  Hereinafter, a logic circuit having a power saving function according to an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the logic circuit 1 includes power supply switching circuits 10A, 10B. . . And circuit modules 20A, 20B. . . A power control circuit 30, an arithmetic processing circuit 40, and a clock generation circuit 50. The power supply switching circuits 10A, 10B. . . Are collectively referred to as the power supply switching circuit 10. The circuit modules 20A, 20B. . . Are collectively referred to as the circuit module 20.

  The circuit module 20 operates by receiving power supply from the power supply line VDDL to which the power supply voltage VDD is applied and the ground power supply line VSSL. The circuit modules 20A and 20B are circuit modules each having a unique function and operating in synchronization with the clock signal CLK, and realize the functions of the entire circuit in cooperation with each other.

  The circuit module 20 has a circuit configuration separated from two viewpoints of a power gating viewpoint and a clock gating viewpoint. That is, the circuit modules 20A, 20B. . . Does not need to be functionally operated at the same time, and forms part of the divided circuit based on the power gating concept.

  Furthermore, the circuit modules 20A, 20B. . . Are circuit modules that are separated to operate according to different clock signals. Circuit modules 20A, 20B. . . Are operated by a single clock signal, and the supply and stop of the clock signal are performed together.

  The power supply switching circuit 10 is a circuit that switches supply and interruption of power to the circuit module 20 based on a control signal supplied from the outside. Power supply switching circuits 10A, 10B. . . Are connected to the circuit modules 20A, 20B. . . A state in which power is supplied to the circuit modules (switch-on), and circuit modules 20A, 20B. . . Switching to the state (switch-off) where the supply of power to the is cut off.

  Power supply switching circuits 10A, 10B. . . Are OR gates 11A, 11B. . . And power switches 12A, 12B. . . With. In the following description, the OR gates 11A, 11B. . . Are collectively referred to as OR gate 11. Similarly, the power switches 12A, 12B. . . Are collectively referred to as the power switch 12.

  The OR gate 11 includes a non-inverting input terminal, an inverting input terminal, and an inverting output terminal.

  A power control signal PG (power gating signal) is input from the power control circuit 30 to the non-inverting input terminal of the OR gate 11. The power control signal PG is at H level (high level) when power supply to the circuit module 20 is stopped, and is at L level (low level) when power is supplied.

  A clock control signal CEN (clock enable signal) is input from the arithmetic processing circuit 40 to the inverting input terminal of the OR gate 11. The clock control signal CEN is a signal that becomes H level when the clock signal CLK supplied to the circuit module 20 is validated and becomes L level when the clock signal CLK is invalidated (not supplied).

  The OR gate 11 outputs an H level signal when the power control signal PG is at the H level or the clock control signal CEN is at the L level, and is output when the power control signal PG is at the L level and the clock control signal CEN is at the H level. A level signal is output.

  The power switch 12 is composed of a P-channel MOSFET (Metal Oxide Semiconductor Field-Effect Transistor), one end (source) of the current path is connected to the power line VDDL, and the other end (drain) of the current path is the circuit module 20 (FIG. 3 is connected to the power supply terminal of the virtual power supply line VVDDL of the circuit module 20 shown in FIG. 3, and the control terminal (gate) is connected to the inverted output terminal of the OR gate 11. Therefore, as shown in FIG. 2, when the output of the OR gate 11 is at the L level (that is, the power control signal PG instructs the supply of power and the clock control signal CEN instructs the supply of the clock signal). The power is supplied to the circuit module 20 from the power line VDDL. Further, the power switch 12 is used when the output of the OR gate 11 is at the H level (that is, when the power control signal PG instructs the non-supply of the power or when the clock control signal CEN instructs the non-supply of the clock signal). Turn off and stop supplying power.

  The power supply control circuit 30 is composed of, for example, a PMU (Power Management Unit). The power supply control circuit 30 monitors the usage status of each circuit module 20 and generates an L-level power supply control signal PG for the circuit module 20 that is determined to be used (power supply is required). An H level power supply control signal PG is generated in the determined circuit module 20 and supplied to the non-inverting input terminal of the corresponding OR gate 11. The power supply control signal PG is a signal on the order of several μs (microseconds) to several ms (milliseconds), and has a coarser granularity than the clock control signal CEN.

  The arithmetic processing circuit 40 is composed of, for example, a CPU (Central Processing Unit). The arithmetic processing circuit 40 determines whether to enable or disable the clock signal CLK by analyzing an operation program or the like, and enables the clock signal CLK based on the determination result. The clock control signal CEN at the H level is supplied to the circuit module 20 determined to be (supplied with the clock signal CLK), and the clock control signal at the L level is supplied to the circuit module 20 determined to be invalid (not supplied). Supply CEN. The arithmetic processing circuit 40 supplies the clock control signal CEN generated for each circuit module 20 to the inverting input terminal of the OR gate 11 corresponding to each circuit module 20.

  As shown in FIG. 3, the circuit module 20 includes an AND gate 21, nonvolatile memory circuits 22 and 23, and a combinational circuit 24. AND gate 21, nonvolatile memory circuits 22, 23, and combinational circuit 24 are connected to virtual power supply line VVDDL and ground power supply line VSSL. When the power switch 12 is switched on, the virtual power supply VVDD is supplied from the virtual power supply line VVDDL to the AND gate 21, the nonvolatile memory circuits 22 and 23, and the combinational circuit 24. The circuit module 20 needs to store internal memory information even when the power switch 12 is switched off and the power is shut off. In a volatile memory circuit such as SRAM (Static Random Access Memory) or DRAM (Dynamic Random Access Memory), when the power is cut off, internal memory information is lost. Therefore, the circuit module 20 does not include a volatile memory circuit.

  The AND gate 21 functions as a clock gating circuit. One non-inverting input terminal of the AND gate 21 is connected to the clock generation circuit 50 through a signal line, and the clock signal CLK supplied from the clock generation circuit 50 is input thereto. The clock generation circuit 50 is composed of, for example, a PLL (Phase Locked Loop) circuit. The clock signal CLK is a signal for operating the entire circuit module 20 and is generated by the clock generation circuit 50.

  The clock generation circuit 50 generates a clock signal CLK having a constant frequency, for example, with a rectangular wave having a duty ratio of 50%, and supplies the clock signal CLK to one input terminal of the AND gate 21. The clock control signal CEN generated by the arithmetic processing circuit 40 is input to the other input terminal of the AND gate 21.

  The AND gate 21 obtains a logical product of the clock signal CLK and the clock control signal CEN, and outputs a logical signal representing the result. That is, the AND gate 21 supplies the clock signal CLK to the nonvolatile memory circuits 22 and 23 only during a period when the clock control signal CEN (H level clock control signal CEN) for enabling the clock signal CLK is input.

  The non-volatile memory circuit 22 is for input and is composed of a non-volatile flip-flop. The non-volatile memory circuit 22 latches the input signal of the circuit module 20 in response to the rising edge of the clock signal output from the AND gate 21, and the combination of the subsequent stages Supply to circuit 24.

  The combination circuit 24 performs a logical operation on the data output from the nonvolatile memory circuit 22 and outputs the logical operation to the nonvolatile memory circuit 23. The combinational circuit 24 may include a sequential circuit. However, all the flip-flops constituting the sequential circuit operate in response to the clock signal output from the AND gate 21. When the flip-flops constituting the sequential circuit are non-volatile, the stored contents can be reproduced when the power is supplied again even if the power supply is stopped. On the other hand, if the flip-flops constituting the sequential circuit are volatile, the stored contents cannot be reproduced when the power is resupplied if the power supply is stopped. Therefore, when a sequential circuit includes a volatile flip-flop, the sequential circuit is used for temporarily holding data.

  The non-volatile memory circuit 23 is for output and is composed of a non-volatile flip-flop. The non-volatile memory circuit 23 latches the output signal of the combinational circuit 24 in response to the rising edge of the clock signal output from the AND gate 21, and the circuit module. 20 output signals are output.

  The structure of the nonvolatile memory elements constituting the nonvolatile memory circuits 22 and 23 is arbitrary, but a nonvolatile memory element using a magnetic tunnel junction element (MTJ: Magnetic Tunneling Junction, hereinafter referred to as MTJ element) is suitable. . Although this type of nonvolatile semiconductor element is not limited, for example, a nonvolatile memory element described in JP2012-242287A can be used. In a variable resistance nonvolatile memory element such as a memory including a variable resistance element such as an MTJ element, a subthreshold current (weak inversion current) of a driving MOSFET flows through the MTJ element, so that the MTJ element functions. Leakage current may occur even when not. That is, the leakage current cannot be suppressed only by closing the AND gate 21 with the clock control signal CEN (by simply stopping the clock). In this embodiment, the AND gate 21 is closed and the power supply itself is stopped by the clock control signal CEN, so that it is possible to contribute to a reduction in power consumption of a circuit having a nonvolatile element in which leakage current is unavoidable. In addition, as a non-volatile element other than the MTJ element, a ferroelectric (Ferro Electric) element or the like may be employed.

Next, the operation of the logic circuit having the above configuration will be described.
In a normal state, the L-level power supply control signal PG_A and the H-level clock control signal CEN_A are supplied to the OR gate 11A, and the OR gate 11A outputs an L-level signal. For this reason, the power switch 12A is turned on, and power is supplied to the circuit module 20A. The AND gate 21 in the circuit module 20A outputs the clock signal CLK because the clock control signal CEN_A is at the H level. The circuit module 20A performs arithmetic processing in response to the clock signal using the supplied power supply. The same applies to the circuit module 20B.

  Here, for example, it is assumed that the arithmetic processing circuit 40 detects that the processing of the circuit module 20A should be temporarily stopped. In this case, the arithmetic processing circuit 40 switches the clock control signal CEN_A supplied to the circuit module 20A to L level. As a result, the AND gate 21 in the circuit module 20A closes the gate and does not output the clock signal CLK. For this reason, the circuit module 20A temporarily stops its operation. At the same time, the output of the OR gate 11A becomes H level, and the power switch 12A is turned off. For this reason, power supply to the circuit module 20A is stopped, and power consumption is suppressed. Thereafter, when the processing proceeds and the arithmetic processing circuit 40 determines that the operation of the circuit module 20A is necessary, the arithmetic processing circuit 40 switches the clock control signal CEN_A to the H level. As a result, the output of the OR gate 11A becomes L level, the power switch 12A is turned on, and the power supply to the circuit module 20B is resumed. Since the circuit module 20A includes the nonvolatile storage circuits 22 and 23, there is no problem that the storage state becomes indefinite when the power is resupplied. The internal state of the combinational circuit 24 is also restored from the output of the nonvolatile memory circuit 22 to the state when the power is shut off. In parallel, when the clock control signal CEN_A becomes H level, the AND gate 21 in the circuit module 20A opens the gate, and the circuit module 20A resumes normal operation according to the clock signal CLK.

  When the power supply control circuit 30 determines that the circuit module 20A is not operating, the power supply control circuit 30 switches the power supply control signal PG_A to the H level. As a result, the output of the OR gate 11A becomes H level, the power switch 12A is turned off, and the power supply to the circuit module 20A is stopped. Thereafter, when the power supply control circuit 30 determines that the operation of the circuit module 20A is necessary, the power supply control signal PG_A is switched to the L level. Thereby, the output of the OR gate 11A becomes L level, the power switch 12A is turned on, and the power supply to the circuit module 20A is resumed. As described above, since the circuit module 20A includes the nonvolatile storage circuits 22 and 23, there is no problem that the storage state becomes indefinite when the power is supplied again. The internal state of the combinational circuit 24 is also restored from the output of the nonvolatile memory circuit 22 to the state when the power is shut off. Thereafter, the circuit module 20A resumes normal operation.

  As described above, according to the power supply switching circuit 10 according to the present embodiment, the supply and cut-off of power to the circuit module 20 are switched based on one clock control signal CEN supplied to each circuit module 20. . As shown in FIG. 4A, when the clock control signal CEN is at the L level (when the circuit module 20 does not perform a substantial operation), the power supply switching circuit 10 supposes that the power supply switching circuit 10 Even if the supply is instructed, the power supply to the circuit module 20 is stopped. As a result, as shown in FIG. 4B, lower power consumption is achieved more efficiently than when power supply to the circuit module 20 is stopped based only on the power control signal PG supplied from the power control circuit. be able to. Further, according to the power supply switching circuit 10, the power supply can be switched in units of the circuit module 20 (function) regardless of the circuit size of the circuit module 20, and the circuit configuration for controlling the power supply can be simplified.

  Further, the power supply switching circuit 10 switches between supply and cut-off of power to the circuit module 20 based on one power supply control signal PG supplied for each circuit module 20. As a result, the power supplied to the circuit module 20 can also be controlled by the power control signal PG, and more efficient and low power consumption can be achieved.

  As shown in FIG. 5, the logic gate included in the power supply switching circuit 10 includes an AND gate 13 in which the clock control signal CEN is input to the non-inverting input terminal and the power supply control signal PG is input to the inverting input terminal. May be. The input / output logic of the AND gate 13 is the same as that of the OR gate 11.

  Further, as shown in FIG. 6, the power supply switching circuit 10 may include only the power switch 12 that does not include the OR gate 11 and maintains the switch on / off state based only on the clock control signal CEN. In this case, when the clock control signal CEN whose signal level is L level is input to the gate of the power switch 12, the power switch 12 remains switched on and the signal level is H level to the gate of the power switch 12. When the clock control signal CEN is input, the power switch 12 remains switched off.

  Further, as shown in FIG. 7, the power supply switching circuit 10 may be provided between the circuit module 20 and the ground power supply line VSSL that supplies the ground power supply VSS. As shown in FIG. 7, the power supply switching circuit 10 includes a power switch 14 composed of an N-channel MOSFET and an OR gate 15. Also in this case, as in the above embodiment, when the clock control signal CEN input to the OR gate 15 instructs the supply of the clock (enables the clock) and the power control signal PG instructs the supply of power, The power switch 14 maintains a switch-on state, and power is supplied to the circuit module 20. In other cases, the power switch 14 maintains a switch-off state, and the power to the circuit module 20 is cut off.

  In addition, the present invention is not limited by the description of the above-described embodiment and the drawings, and appropriate modifications and the like can be added to the above-described embodiment and the drawings.

  For example, another signal may be supplied as an input signal to the OR gate 11. That is, other conditions may be considered in order to control the power switch 12.

  Although an example in which a MOS transistor is used as the power switch 12 is shown, any configuration may be used as long as the switch element can be controlled by the output of the logic circuit.

  A typical configuration of the circuit module 20 is shown in FIG. 3, but is not limited thereto. However, the configuration in which the non-volatile memory circuits 22 and 23 are arranged in the input stage and the output stage, and the combinational circuit 24 is arranged between them, so that there is no inconvenience due to power gating (for example, the memory state is indefinite when power is resupplied) Therefore, the logic circuit can be operated.

  The power supply switching circuit 10 may be configured such that the clock control signal CEN is input to the OR gate 11 after the clock control signal CEN is input to the AND gate 21. For example, the clock control signal CEN via a delay circuit may be input to the OR gate 11. This prevents the power supplied to the circuit module 20 from being shut off before data is stored (latched) in the nonvolatile memory circuits 22 and 23, and the internal memory information can be stored safely.

  In the above embodiment, power is supplied when the power control signal PG is at H level, power is not supplied when it is at L level, clock signal is supplied when the clock control signal CEN is at H level, and clock is not supplied when it is at L level. However, these logics can be arbitrarily changed.

DESCRIPTION OF SYMBOLS 1 Logic circuit 10 (10A, 10B) Power supply switching circuit 11 (11A, 11B), 15 OR gate (gate means)
12 (12A, 12B), 14 Power switch (switch means)
13 AND gate (gate means)
20, 20A, 20B Circuit module 21 AND gate 22, 23 Non-volatile memory circuit 24 Combination circuit 30 Power supply control circuit 40 Arithmetic processing circuit 50 Clock generation circuit VDD power supply VSS Ground power supply VVDD Virtual power supply VDDL Power supply line VSSL Ground power supply line VVDDL Virtual power supply Line CLK Clock signal CEN, CEN_A, CEN_B Clock control signal PG, PG_A, EN_B Power control signal

Claims (4)

Based on a clock control signal for setting the clock signal to be valid or invalid, a clock signal output means for outputting the clock signal, a nonvolatile memory element that operates in response to the clock signal output from the clock signal output means, A circuit module comprising:
A first state that is provided between the power supply line and the circuit module, and that supplies power to the circuit module from the power supply line, and a second state that blocks supply of power from the power supply line to the circuit module. Switch means for setting based on the clock control signal,
A logic circuit characterized by that. The switch means maintains the first state when a clock control signal for validly setting the clock signal of the circuit module is input, and receives a clock control signal for invalidating the clock signal of the circuit module. If so, maintain the second state,
The logic circuit according to claim 1. Furthermore, a logic operation circuit that performs a logic operation of the power control signal that instructs the supply and stop of power to the circuit module and the clock control signal,
The logic operation circuit sets the switch means to the first state when the power control signal instructs supply of power and the clock control signal sets the clock signal of the circuit module to be valid;
The logic circuit according to claim 1, wherein The circuit module includes an input nonvolatile memory circuit that captures and outputs an input signal in response to the clock signal, and a combinational circuit that performs a logical operation based on data stored in the input nonvolatile memory circuit And an output non-volatile memory circuit that stores and outputs the output of the combinational circuit in response to the clock signal,
4. The logic circuit according to claim 1, wherein the logic circuit is any one of the above.

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