Leakage current reduction in a sequential circuit

• US 8,736,332 B2
• Filed: 12/17/2009
• Issued: 05/27/2014
• Est. Priority Date: 12/17/2009
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: LSI Corporation (Broadcom, Inc.)
• Inventors: Sriadibhatla, Srinivas
• Primary Examiner(s): Chen, Sibin
• Application Number:
  US12/640,004
• Publication Number:
  US 20110148496A1
• Time in Patent Office: 1,622 Days
• Field of Search: 327199-203, 327/208, 327210-212, 327/215, 327217-219, 327/544, 326/40, 326/46
• US Class Current: 327/199
• CPC Class Codes: H03K 19/0008 Arrangements for reducing power consumption
• CPC Class Codes: H03K 3/012 Modifications of generator to improve response time or to decrease power consumption

Abstract

A system and device for reducing leakage current in a sequential circuit is disclosed. In one embodiment, a system for reducing leakage current in a sequential circuit includes a combinational logic circuit, one or more reset flip-flops coupled to the combinational logic circuit, and one or more set-reset flip-flops coupled to the combinational logic circuit. The system further includes a control module coupled to the reset flip-flops and to the set flip-flops and configured to reset the reset flip-flops and to set the set-reset flip-flops when a standby mode of the sequential circuit is triggered.

Claims

1. A device comprising a sequential circuit having an active mode and a standby mode, the sequential circuit comprising:

a first combinational logic circuit;

a first set of one or more reset flip-flops, each reset flip-flop having (i) a data input port, (ii) a reset port, and (iii) a data output port coupled to a corresponding data input port of the first combinational logic circuit;

a first set of one or more set-reset flip-flops, each set-reset flip-flop having (i) a data input port, (ii) a set port, (iii) a reset port, and (iv) a data output port coupled to a corresponding data input port of the first combinational logic circuit, wherein the first combinational logic circuit provides reduced leakage current when (i) each reset flip-flop provides a data value of 0 and (ii) each set-reset flip-flop provides a data value of 1 to the corresponding data input ports of the first combinational logic circuit; and

a control module coupled to the one or more reset flip-flops and to the one or more set-reset flip-flops, wherein the control module is configured to;

apply active-mode data values presented at the data input ports of (i) the one or more reset flip-flops and (ii) the one or more set-reset flip-flops to the corresponding data input ports of the first combinational logic circuit during the active mode of the sequential circuit; and

(i) reset the one or more reset flip-flops such that the data output port of each reset flip-flop applies a data value of 0 to the corresponding data input port of the first combinational logic circuit and (ii) set the one or more set-reset flip-flops such that the data output port of each set-reset flip-flop applies a data value of 1 to the corresponding data input port of the first combinational logic circuit during the standby mode of the sequential circuit to configure the first combinational logic circuit to provide the reduced leakage current.

2. The device of claim 1, wherein the one or more reset flip-flops comprise at least one asynchronous reset flip-flop, and wherein the one or more set-reset flip-flops comprise at least one asynchronous set-reset flip-flop.

3. The device of claim 1, wherein the one or more reset flip-flops comprise at least one synchronous reset flip-flop, and wherein the one or more set-reset flip-flops comprise at least one synchronous set-reset flip-flop.

4. The device of claim 1, wherein each reset flip-flop and each set-reset flip-flop is based on a D-type flip-flop.

5. The device of claim 1, further comprising a power management unit coupled to the control module to forward a sleep signal when the standby mode of the sequential circuit is triggered.

6. The device of claim 1, wherein the one or more reset flip-flops and the one or more set-reset flip-flops are configured to feed minimum leakage bits for the first combinational logic circuit during the standby mode.

7. The device of claim 6, wherein the minimum leakage bits are used to provide minimum leakage current via the first combinational logic circuit.

8. The device of claim 6, wherein the minimum leakage bits are obtained using an input vector control method.

9. The device of claim 1, wherein the control module comprises:

an OR gate coupled to (i) receive an active-mode set signal and a sleep signal and (ii) provide an OR-gate output signal to the set port of each set-reset flip-flop, such that, when the sleep signal indicates that the sequential circuit is in the standby mode, the OR-gate output signal ensures that each set-reset flip-flop applies a data value of 1 to the corresponding data input port of the first combinational logic circuit; and

an AND gate coupled (i) receive an active-mode reset signal and the sleep signal and (ii) provide an AND-gate output signal to the reset port of each reset flip-flop, such that, when the sleep signal indicates that the sequential circuit is in the standby mode, the AND-gate output signal ensures that each reset flip-flop applies a data value of 0 to the corresponding data input port of the first combinational logic circuit.

10. The device of claim 9, wherein:

the sleep signal is an active low signal; and

the OR gate is configured to set each set-reset flip-flop based on the active low sleep signal received when the standby mode of the sequential circuit is triggered.

11. The device of claim 10, wherein the OR gate comprises a first input node and a second input node, and wherein the OR gate is configured to invert and process the active low sleep signal via the second input node.

12. The device of claim 11, wherein the OR gate is configured to invert and process a high sleep signal via the second input node when the active mode of the sequential circuit is triggered.

13. The device of claim 9, wherein:

the sleep signal is an active low signal; and

the AND gate is configured to reset each reset flip-flop based on the active low sleep signal received when the standby mode of the sequential circuit is triggered.

14. The device of claim 13, wherein the AND gate comprises a first input terminal and a second input terminal, and wherein the AND gate is configured to process the active low sleep signal via the first terminal.

15. The device of claim 14, wherein the AND gate is configured to process a high sleep signal via the first input terminal when the active mode of the sequential circuit is triggered.

16. The device of claim 1, wherein the sequential circuit further comprises one or more other combinational logic circuits, one or more other sets of one or more reset flip-flops, and one or more other sets of set-reset flip-flops, sequentially configured with the first combinational logic circuit, the first set of one or more reset flip-flops, and the first set of one or more set-reset flip-flops, wherein:

each other set of one or more reset flip-flops and each other set of one or more set-reset flip-flops are configured to a corresponding other combinational logic circuit and to the control module in a manner analogous to how the first set of one or more reset flip-flops and the first set of one or more set-reset flip-flops are configured to the first combinational logic circuit and to the control module.