Sense amplifier based flip-flop

• US 7,692,466 B2
• Filed: 08/18/2006
• Issued: 04/06/2010
• Est. Priority Date: 08/18/2006
• Status: Expired due to Fees

• Current Assignee: ATI Technologies Incorporated (Advanced Micro Devices, Inc.)
• Original Assignee: ATI Technologies ULC (Advanced Micro Devices, Inc.)
• Inventors: Ahmadi, Rubil
• Primary Examiner(s): Donovan; Lincoln
• Assistant Examiner(s): CHENG, DIANA
• Application Number:
  US11/465,590
• Publication Number:
  US 20080042713A1
• Time in Patent Office: 1,327 Days
• Field of Search: 327/217, 327/218, 327/208, 327/210, 327/199, 327/214, 327/215, 327/276, 327/281
• US Class Current: 327/218
• CPC Class Codes: G11C 7/062 Differential amplifiers of non-latching type, e.g. comparators, long-tailed pairs
• CPC Class Codes: G11C 7/065 Differential amplifiers of latching type
• CPC Class Codes: H03K 3/356139 with synchronous operation

Abstract

A circuit includes an input stage, an output stage, and a delay stage. The input stage is operative to receive a clock signal and a first and second input signal. The output stage is operative to receive the clock signal. The output stage is also operative to generate a first and second output signal based on the clock signal and the first and second input signals. The delay stage is operatively coupled to the input and output stages. The delay stage includes a first and second branch. The second branch includes at least one more delay element than the first branch.

Claims

1. A circuit comprising:

an input stage that is operative to receive a clock signal and a first and second input signal;

an output stage that is operative to receive the clock signal and to generate a first and second output signal based on the clock signal and the first and second input signals; and

a delay stage that is operatively coupled to the input and output stages and that comprises a first and second branch, wherein the second branch includes at least one more delay element than the first branch.

2. The circuit of claim 1 wherein:

the first branch comprises a first transistor having a first terminal operatively coupled to the output stage, a second terminal operatively coupled to the input stage, and a third terminal operatively coupled to the output stage; and

the second branch comprises a second transistor having a fourth terminal, a fifth terminal operatively coupled to the input stage, and a sixth terminal operatively coupled to the output stage and a third transistor having a seventh terminal operatively coupled to the output stage and an eighth terminal operatively coupled to the fourth terminal.

3. The circuit of claim 1 wherein the delay element comprises a metal oxide semiconductor field effect transistor, the first input signal is an inverse of the second input signal, and the first output signal is a set signal and the second signal is a reset signal.

4. The circuit of claim 1 further comprising a latch stage operatively coupled to the output stage that is operative to generate an output signal based on the first and second output signals.

5. The circuit of claim 4 wherein when the clock signal is low, a first portion of said latch stage is off and a second portion is on.

6. The circuit of claim 5 wherein during a rising edge of the clock signal and when the first input signal is high, the first portion of the latch stage turns on and the second portion turns off.

7. The circuit of claim 4 wherein the latch stage is one of a set-reset latch and an inverted set-reset latch.

8. The circuit of claim 4 wherein the latch stage is operative to generate the output signal after a first delay when the first output signal transitions to one of a high and low level and to generate the output signal after a second delay that is greater than the first delay when the second output signal transitions to one of a high and low level.

9. The circuit of claim 8 wherein the output stage generates the first output signal after the second delay and the second output signal after the first delay.

10. The circuit of claim 1 wherein the input stage comprises:

a first transistor having a first, second, and third terminal, wherein the first terminal is operatively coupled to the first branch and the third terminal is operative to receive the first input signal;

a second transistor having a fourth and fifth terminal, wherein the fourth terminal is operatively coupled to the first terminal and the fifth terminal is operatively coupled to the second branch;

a third transistor having a sixth, seventh and eighth terminal, wherein the sixth terminal is operatively coupled to the filth terminal, the seventh terminal is operatively coupled to the second terminal, and the eight terminal is operatively coupled to the second input signal; and

a fourth transistor having a ninth and tenth terminal, wherein the ninth terminal is operatively coupled to the second and seventh terminals and the tenth terminal is operative to receive the clock signal.

11. The circuit of claim 1 wherein the output stage comprises:

a first transistor having a first terminal, a second terminal operative to provide the first output signal, and a third terminal operative to receive the clock signal;

a second transistor having a fourth terminal operatively coupled to the first terminal, a fifth terminal operatively coupled to the second terminal and to the delay stage, and a sixth terminal operatively coupled to the delay stage;

a third transistor having a seventh terminal operatively coupled to the fourth terminal, an eighth terminal operatively coupled to the sixth terminal, and ninth terminal operatively coupled to the fifth terminal; and

a fourth transistor having a tenth terminal operatively coupled to the seventh terminal, an eleventh terminal operatively coupled to the eighth terminal and a twelfth terminal is operative to receive the clock signal.

12. An Integrated circuit comprising:

a latch state that is operative to generate an output in response to a first and second input, wherein the output is generated in response to the first input after a first delay and the output is generated in response to the second input after a second delay that is greater than the first delay; and

a sense amplifier stage that is operative to generate the first and second inputs in response to a clock signal, wherein the first input is generated after the second delay and the second input is generated after the first delay, wherein the sense amplifier stage comprises a delay stage that comprises a first branch that is operative to provide the first delay and a second branch that is operative to provide the second delay and wherein the second branch includes at least one more delay element than the first branch.

13. The integrated circuit of claim 12 wherein:

the first branch comprises a first transistor having a first terminal operatively coupled to the output stage, a second terminal operatively coupled to the input stage, and a third terminal operatively coupled to the output stage; and

the second branch comprises a second transistor having a fourth terminal, a fifth terminal operatively coupled to the input stage, and a sixth terminal operatively coupled to the output stage and a third transistor having a seventh terminal operatively coupled to the output stage and an eighth terminal operatively coupled to the fourth terminal.

14. The integrated circuit of claim 12 wherein the delay element comprises a metal oxide semiconductor field effect transistor.

15. A flip-flop comprising:

an output stage that comprises;

a first transistor having a first terminal operatively coupled to a voltage source, a second terminal, and a third terminal that is operative to receive a clock signal,

a second transistor having fourth terminal operatively coupled to the first terminal, a fifth terminal operatively coupled to the second terminal, and a sixth terminal;

a third transistor having a seventh terminal operatively coupled to the fourth terminal, an eighth terminal operatively coupled to the sixth terminal, and a ninth terminal operatively coupled to the fifth terminal; and

a fourth transistor having a tenth terminal operatively coupled to the seventh terminal, an eleventh terminal operatively coupled to the eighth terminal, and a twelfth terminal that is operative to receive the clock signal;

a delay stage that comprises a first and second branch, wherein the second branch includes at least one more delay element than the first branch,

wherein the first branch comprises;

a fifth transistor having a thirteenth terminal operatively coupled to the fifth terminal, a fourteenth terminal operatively coupled to an input stage, and a fifteenth terminal operatively coupled to the sixth terminal, and

wherein the second branch comprises;

a sixth terminal having an sixteenth terminal, a seventeenth terminal operatively coupled to the input stage, and an eighteenth terminal operatively coupled to the ninth terminal, and

a seventh transistor having a nineteenth terminal operatively coupled to the eighth terminal, a twentieth terminal operatively coupled to the sixteenth terminal, and a twenty-first terminal operatively couple to the voltage source; and

a latch stage operatively coupled to the second and eleventh terminals.

16. The flip-flop of claim 15 further comprising an input stage that comprises:

an eighth transistor having a twenty-second terminal operatively coupled to the fourteenth terminal, a twenty-third terminal, and a twenty-fourth terminal that is operative to receive an input signal;

a ninth transistor having a twenty-fifth terminal operatively coupled to the twenty-second terminal, a twenty-sixth terminal operatively coupled to the seventeenth terminal, and a twenty-seventh terminal operatively coupled to the voltage source;

a tenth transistor having a twenty-eighth terminal, operatively coupled to the twenty-sixth terminal, a twenty-ninth terminal operatively coupled to the twenty-third terminal, and a thirtieth terminal that is operative a receive an inverse of the input signal; and

an eleventh transistor having a thirty-first terminal operatively coupled to the twenty-ninth terminal, a thirty-second terminal that is operative to receive the clock signal, and a thirty-third terminal operatively coupled to a second voltage source that is less that the voltage source.

17. The flip-flop of claim 16 wherein the first, second, third, and fourth transistors are p-channel metal oxide semiconductor field effect transistors.

18. The hip-flop of claim 16 wherein the fifth, sixth, seventh, eighth, ninth, tenth, and eleventh transistors are n-channel metal oxide semiconductor field effect transistors.

19. A device comprising an integrated circuit that comprises:

a latch stage that is operative to generate an output in response to a first and second input, wherein the output is generated in response to the first input after a first delay and the output is generated in response to the second input after a second delay that is greater than the first delay;

a sense amplifier stage that is operative to generate the first and second inputs in response to a clock signal, wherein the first input is generated after the second delay and the second input is generated after the first delay, wherein the sense amplifier stage comprises a stage that comprises a first branch that is operative to provide the first delay and a second branch that is operative to provide the second delay and wherein the second branch includes at least one more delay element than the first branch.

20. The device of claim 19 further comprising a display that communicates with the integrated circuit via a bus, wherein the integrated circuit is at least one of:

a processor and memory.

21. The device of claim 19 wherein when the clock signal is low, a first portion of said latch stage is off and a second portion is on.

22. The device of claim 21 wherein during a rising edge of the clock signal and when the first input signal is high, the first portion of the latch stage turns on and the second portion turns off.

23. An integrated circuit design system comprising:

a processor; and

memory operatively coupled to the processor that comprises a circuit design cell, comprising;

a latch stage that is operative to generate an output in response to a first and second input, wherein the output is generated in response to the first input after a first delay and the output is generated in response to the second input after a second delay that is greater than the first delay; and

a sense amplifier stage that is operative to generate the first and second inputs in response to a clock signal, wherein the first input is generated after the second delay and the second input is generated after the first delay, wherein the sense amplifier stage comprises a delay stage that comprises a first branch that is operative to provide the first delay and a second branch that is operative to provide the second delay and wherein the second branch includes at least one more delay element than the first branch.

24. A computer readable media storing instructions, said instructions adapted to provide a cell library, said cell library comprising data representing:

an input stage that is operative to receive a clock signal and a first and second input signal;

an output stage that is operative to receive the clock signal and to generate a first and second output signal based on the clock signal and the first and second input signals; and

a delay stage that is operatively coupled to the input and output stages and that comprises a first and second branch, wherein the second branch includes at least one more delay element than the first branch.

25. The computer readable media of claim 24 containing data representing the cell library that contains data representing:

the first branch comprises a first transistor having a first terminal operatively coupled to the output stage, a second terminal operatively coupled to the input stage, and a third terminal operatively coupled to the output stage; and

the second branch comprising a second transistor having a fourth terminal, a fifth terminal operatively coupled to the input stage, and a sixth terminal operatively coupled to the output stage and a third transistor having a seventh terminal operatively coupled to the output stage and an eighth terminal operatively coupled to the fourth terminal.

26. The computer readable media of claim 24 containing data representing the cell library that contains data representing:

a first transistor having a first, second, and third terminal, wherein the first terminal is operatively coupled to the first branch and the third terminal is operative to receive the first input signal;

a second transistor having a fourth and fifth terminal, wherein the fourth terminal is operatively coupled to the first terminal and the fifth terminal is operatively coupled to the second branch;

a third transistor having a sixth, seventh and eight terminal, wherein the sixth terminal is operatively coupled to the fifth terminal, the seventh terminal is operatively coupled to the second terminal, and the eight terminal is operatively coupled to the second input signal; and

a fourth transistor having a ninth and tenth terminal, wherein the ninth terminal is operatively coupled to the second and seventh terminals and the tenth terminal is operative to receive the clock signal.

27. The computer readable media of claim 24 containing data representing the cell library that contains data representing:

a first transistor having a first terminal, a second terminal operative to provide the first output signal, and a third terminal operative to receive the clock signal;

a second transistor having a fourth terminal operatively coupled to the first terminal, a fifth terminal operatively coupled to the second terminal and to the delay stage, and a sixth terminal operatively coupled to the delay stage;

a third transistor having a seventh terminal operatively coupled to the fourth terminal, an eighth terminal operatively coupled to the sixth terminal, and ninth terminal operatively coupled to the fifth terminal; and

a fourth transistor having a tenth terminal operatively coupled to the seventh terminal, an eleventh terminal operatively coupled to the eighth terminal and a twelfth terminal is operative to receive the clock signal.

28. A computer readable media storing instructions, that when executed, provide a circuit design program that uses a cell library that comprises a data representing:

a latch stage that is operative to generate an output in response to a first and second input, wherein the output is generated in response to the first input after a first delay and the output is generated in response to the second input after a second delay that is greater than the first delay; and

a sense amplifier stage that is operative to generate the first and second inputs in response to a clock signal, wherein the first input is generated after the second delay and the second input is generated after the first delay, wherein the sense amplifier stage comprises a delay stage that comprises a first branch that is operative to provide the first delay and a second branch that is operative to provide the second delay and wherein the second branch includes at least one more delay element than the first branch.

29. The computer readable media storing instructions of claim 28 wherein the data representing the sense amplifier stage includes data representing:

an input stage that is operative to receive a clock signal and a first and second input signal;

an output stage that is operative to receive the clock signal and to generate a first and second output signal based on the clock signal and the first and second input signals; and

the delay stage operatively coupled to the input and output stages.

30. The computer readable media storing instructions of claim 28 wherein the data representing the sense amplifier stage includes data representing:

the first branch that comprises a first transistor having a first terminal operatively coupled to the output stage, a second terminal operatively coupled to the input stage, and a third terminal operatively coupled to the output stage; and

the second branch that comprises a second transistor having a fourth terminal, a fifth terminal operatively coupled to the input stage, and a sixth terminal operatively coupled to the output stage and a third transistor having a seventh terminal operatively coupled to the output stage and an eighth terminal operatively coupled to the fourth terminal.

31. The computer readable media storing instructions of claim 28 wherein the data representing the sense amplifier stage includes data representing:

a first transistor having a first, second, and third terminal, wherein the first terminal is operatively coupled to the first branch and the third terminal is operative to receive the first input signal;

a second transistor having a fourth and fifth terminal, wherein the fourth terminal is operatively coupled to the first terminal and the fifth terminal is operatively coupled to the second branch;

a third transistor having a sixth, seventh and eighth terminal, wherein the sixth terminal is operatively coupled to the fifth terminal, the seventh terminal is operatively coupled to the second terminal, and the eight terminal is operatively coupled to the second input signal; and

a fourth transistor having a ninth and tenth terminal, wherein the ninth terminal is operatively coupled to the second and seventh terminals and the tenth terminal is operative to receive the clock signal.

32. The computer readable media storing instructions of claim 28 wherein the data representing the sense amplifier stage includes data representing:

a first transistor having a first terminal, a second terminal operative to provide the first output signal, and a third terminal operative to receive the clock signal;

a second transistor having a fourth terminal operatively coupled to the first terminal, a fifth terminal operatively coupled to the second terminal and to the delay stage, and a sixth terminal operatively coupled to the delay stage;

a third transistor having a seventh terminal operatively coupled to the fourth terminal, an eighth terminal operatively coupled to the sixth terminal, and ninth terminal operatively coupled to the fifth terminal; and

a fourth transistor having a tenth terminal operatively coupled to the seventh terminal, an eleventh terminal operatively coupled to the eighth terminal and a twelfth terminal is operative to receive the clock signal.

33. A circuit, comprising:

a sense amplifier stage that comprises;

an input stage that is operative to receive a clock signal and a first and second input signal;

an output stage that is operative to receive the clock signal and to generate a first and second output signal based on the clock signal and the first and second input signals, wherein the first output signal is generated in response to the first input signal after a first delay and the second input signal is generated in response to the second input signal after a second delay that is greater than the first delay; and

a delay stage, operatively coupled to the input and output stages, that comprises a first branch that is operative to provide the first delay and second branch that is operative to provide the second delay, wherein the second branch includes at least one more delay element than the first branch; and

a latch stage, operatively coupled to the output stage, that is operative to generate a third output in response to the first output after the second delay and to generate the third output in response to the second output after a second delay that is greater than the first delay.