High performance dual-stage sense amplifier circuit

• US 6,788,112 B1
• Filed: 05/12/2003
• Issued: 09/07/2004
• Est. Priority Date: 05/12/2003
• Status: Expired due to Fees

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Chan, Yuen H., Pelella, Antonio R., Joshi, Rajiv, Wadhwa, Jatinder K., Rawlins, John R.
• Primary Examiner(s): Callahan, Timothy P.
• Assistant Examiner(s): Luu, An T.
• Application Number:
  US10/436,229
• Time in Patent Office: 484 Days
• Field of Search: 327/51-57, 365/49, 365/222, 365/230.09, 365/189.05
• US Class Current: 327/51
• CPC Class Codes: G11C 11/419 Read-write [R-W] circuits
• 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

Abstract

A sense amplifier for a memory device comprising: a first sensing stage comprising a first sensing device and a second sensing device operably connected to a first sense line and a second sense line respectively, to reduce the capacitive load on the first sense line and second sense line. A source terminal of the sensing device is connected to a switchable current sink with drain terminal thereof connected to an input of a second sensing stage. The sense amplifier also includes a second sensing stage comprising cross-coupled inverters responsive to the first sensing stage, the second sensing stage is activated by a sense enable signal following a selected delay, and an output driver responsive to the second sensing stage.

Claims

1. A sense amplifier for a memory device comprising:

a first sensing stage comprising a first sending device and a second sensing device;

a first sensing line and a second sense line directly connected to a gate of said first sensing device and a gate of said second sensing device, respectively, to reduce capacitive load on said first sense line and said second sense line;

wherein a source terminal of said first sensing device and said second sensing device, respectively, is connected to a switchable current sink and a drain terminal of said first sensing device and said second sensing device, respectively, connected to an input of a second sensing stage;

said second sensing stage comprising cross-coupled inverters responsive to said first sensing stage, said second sensing stage activated by a sense enable signal following a selected delay, wherein said first sensing stage is deactivated once said second sensing stage is activated;

an output driver responsive to said second sensing stage;

wherein said second sensing stage of said sensing stage of said sense amplifier, when activated, provides a feedback signal to deactivate said first sensing stage so that at any time only one of said first sensing stage and said second sensing state is active.

2. The sense amplifier of claim 1 wherein said first sensing stage employs sensing devices exhibiting less capacitance than said second sensing stage and said output driver to reduce current and capacitive loading on said sense lines.

3. The sense amplifier of claim 1 wherein activation of said first sensing stage and second sensing stage of the said sense amplifier are controlled in a sequential manner, wherein said first stage sensing stage is activated and a selected delay later, said second sensing stage is activated.

4. The sense amplifier of claim 3 wherein said selected delay is provided by a pair of CMOS inverters configured to manipulate timing of activation of said second sensing stage.

5. The sense amplifier of claim 1 further including a precharge of selected dynamic nodes of said sense amplifier.

6. A sense amplifier for a memory device comprising:

a first sensing stage comprising a first sending device and a second sensing device;

a first sensing line and a second sense line directly connect to a gate of said first sensing device and a gate of said second sensing device, respectively, to reduce capacitive load on said first sense line and said second sense line;

wherein a source terminal of said first sensing device and said second sensing device, respectively, is connected to a switchable current sink and a drain terminal of said first sensing device and said second sensing device, respectively, connected to an input of a second sensing stage;

said second sensing stage comprising cross-coupled inverters responsive to said first sensing stage, said second sensing stage activated by a sense enable signal following a selected delay, wherein said first sensing stage is deactivated once said second sensing stage is activated;

an output driver responsive to said second sensing stage;

a precharge of selected dynamic nodes of said sense amplifier;

wherein said output driver is a high speed push-pull circuit connected to said second sensing stage, said output driver configured to ensure that said precharge deactivates said output driver, and thereby, said sense amplifier exhibits a high impedance state at an output thereof.

7. A method of detecting a signal on a pair of complementary sense lines in a dual-stage sense amplifier for a memory device comprising:

detecting a differential voltage between a first sense line and a second sense line with a first sensing stage comprising a first sensing device and a second sensing device;

amplifying said differential voltage with a second sensing stage comprising cross-coupled inverters responsive to said first sensing stage, said second sensing stage activated by a sense enable signal following a selected delay, wherein said first sensing stage is deactivated once said second sensing stage is activated;

generating a output signal with as output driver responsive to said second sensing stage; and

deactivating said first sensing stage when said second sensing stage of said sense amplifier is activated so that at any time only one of said first sensing stage and said second sensing stage is active.

8. The method of claim 7 wherein said first sensing stage employs sensing devise exhibiting less capacitance than said second sensing stage and said output driver to reduce current and capacitive loading on said sense lines.

9. The method of claim 7 wherein said amplifying includes generating a substantially rail-to-rail voltage swing to drive said output driver.

10. The method of claim 7 wherein deactivating of said first sensing stage and second sensing stage of the said sense amplifier are controlled in a sequential manner, wherein said first stage sensing stage is activated and a selected delay later, said second sensing stage is activated.

11. The method of claim 7 further including precharging selected dynamic nodes of said sense amplifier.

12. The method of claim 11 wherein said precharging includes voltage equalization between signal phases of said sense lines.

13. A method of detecting a signal an a pair of complementary sense lines in a dual-stage sense amplifier for a memory device comprising;

detecting a differential voltage between a first sense line and a second sense line with a first sensing stage comprising a first sensing device and a second sensing device;

amplifying said differential voltage with a second sensing stage comprising cross-coupled inverters responsive to said first sensing stage, said second sensing stage activated by a sense enable signal following a selected delay, wherein said first sensing stage is deactivated once said second sensing stage is activated;

generating a output signal with an output driver responsive to said second sensing stage;

a precharge of selected dynamic nodes of said sense amplifier, said precharging includes voltage equalization between signal phases of said sensing lines; and

wherein said output driver is a high speed push-pull circuit connected to said second sensing stage, said output driver configured to ensure that said precharging deactivates said output driver, and thereby, said sense amplifier exhibits a high impedance state at an output thereof.

14. A sense amplifier for a memory device comprising:

first sensing stage comprising a first sensing device and a second sensing device;

a first sense line and a second sense line directly connected to a gate of said first sensing device and a gate of said second sensing device, respectively, to reduce capacitive load on said first sense line and said second sense line;

wherein a source terminal of said first sensing device and said second sensing device, respectively, is connected to a switchable current sink and a drain terminal of said first sensing device and said second sensing device, respectively, connected to an input of a second sensing stage;

said second sensing stage comprising a pair of cross-coupled complementary inverters coupled to said switchable current sink, responsive to said first sensing stage and operably connected to said first sense line and said second sense line, said second sensing stage activated by a sense enable signal;

an output driver responsive to said second sensing stage;

a precharge of selected dynamic nodes of said sense amplifier; and

wherein said output driver is a high speed push-pull circuit connected to said second sensing stage, said output driver configured to ensure that said precharged deactivates said output driver, and thereby, said sense amplifier exhibits a high impedance stage at an output thereof.

15. The sense amplifier of claim 14 wherein said current sink concurrently activates both said first sensing stage and said second sensing stage in parallel.

16. The sense amplifier of claim 14 wherein said first sensing stage employs sensing devices exhibiting less capacitance than said second sensing stage and said output driver to reduce current and capacitive loading on said sense lines.

17. The sense amplifier of claim 14 wherein activation of said first sensing stage and second sensing stage of the said sense amplifier are controlled in a concurrent manner, wherein said first sensing stage is activated parallel with said second sensing stage.

18. A sense amplifier for a memory device comprising:

first sensing stage comprising a first sensing device and a second device;

a first sense line and a second sense line directly connected to a gate of said first sensing device and a gate of said second sensing device, respectively, to reduce capacitive load on said first sense line and said second sense line;

wherein a source terminal of said first sensing device and said second sensing device, respectively, is connected to a switchable current sink and a drain terminal of said first sensing device and said second sensing device, respectively, connected to an input of a second sensing stage;

said second sensing stage comprising a pair of cross-coupled complementary inverters coupled to said switchable current sink, responsive to said first sensing stage and operably connected to said first sense line and said second sense line, said second sensing stage activated by a sense enable signal;

an output driver responsive to said second sensing stage;

a precharge of selected dynamic nodes of said sense amplifier; and

wherein said output driver is a pair of high speed CMOS inverter circuits connected to said second sensing stage, said output driver configured to ensure that said precharged deactivates said output driver, and thereby, said sense amplifier exhibits a dynamic true and complement state at an output thereof.

19. A method of detecting a signal on a pair of complementary sense lines in a dual-stage sense amplifier for a memory device comprising:

detecting a differential voltage between a first sense line and a second sense line with a first sensing stage comprising a first sensing device and a second sensing device;

amplifying said differential voltage with a second sensing stage comprising cross-coupled inverters responsive to and in parallel with said first sensing stage, said second sensing stage activated by a sense enable signal;

generating a output signal with as output driver responsive to said second sensing stage; and

wherein said output driver is a high speed push-pull circuit connected to said second sensing stage, said output driver configured to ensure that said precharged deactivates said output driver, and thereby, said sense amplifier exhibits a high impedance state at an output thereof.

20. The method of claim 19 wherein said first sensing stage employs sensing devices exhibiting less capacitance than said second sensing stage and said output driver to reduce current and capacitive loading on said sense lines.

21. The method of claim 19 wherein said amplifying includes generating a substantially rail-to-rail voltage swing to drive said output driver.

22. The method of claim 19 further including activating said first sensing stage concurrently with said second sensing stage of said sense amplifier is activated so that at any time both of said first sensing stage and said second sensing stage are active.

23. The method of claim 19 wherein said activating of said first sensing stage and said second sensing stage are controlled by an input timing signal, said input timing signal is an active low dynamic signal with a selected pulse width.

24. The method of claim 19 further including precharging selected dynamic nodes of said sense amplifier.

25. The method of claim 19 wherein said precharging includes voltage equalization between signal phases of said sense lines.