Memory elements with body bias control

• US 8,081,502 B1
• Filed: 12/29/2008
• Issued: 12/20/2011
• Est. Priority Date: 12/29/2008
• Status: Active Grant

• Current Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Original Assignee: Altera Corporation (Intel Corporation)
• Inventors: Rahim, Irfan, Liu, Jun, Lee, Andy L., Vest, William Bradley, Zhou, Lu, Xiang, Qi, Tung, Jeffrey Xiaoqi, Ratnakumar, Albert, Yu, Yanzhong
• Primary Examiner(s): Zarabian, Amir
• Assistant Examiner(s): Graham, Kretelia
• Application Number:
  US12/345,560
• Time in Patent Office: 1,086 Days
• Field of Search: 365/154, 365/156, 365/72, 365/190, 365/189.09
• US Class Current: 365/154
• CPC Class Codes: G11C 11/412 using field-effect transistors only

Abstract

An integrated circuit with memory elements is provided. The memory elements may have memory element transistors with body terminals. Body bias control circuitry may supply body bias voltages that strengthen or weaken memory element transistors to improve read and write margins. The body bias control circuitry may dynamically control body bias voltages so that time-varying body bias voltages are supplied to memory element transistors. Address transistors and latch transistors in the memory elements may be selectively strengthened and weakened. Process variations may be compensated by weakening fast transistors and strengthening slow transistors with body bias adjustments.

Claims

1. Circuitry comprising:

a memory cell comprising;

an address transistor with a body terminal; and

first and second cross-coupled inverters, each inverter having an n-channel metal-oxide-semiconductor transistor, a p-channel metal-oxide-semiconductor transistor, and an input, wherein the address transistor is coupled to the input of the first inverter, wherein each of the n-channel metal-oxide-semiconductor transistors has a respective body terminal and wherein each of the p-channel metal-oxide semiconductor transistors has a respective body terminal; and

body bias control circuitry that is operable to supply a dynamic time-varying body bias voltage to the body terminal of the address transistor, wherein the body bias control circuitry is configured to supply body bias voltages to the body terminals of the n-channel metal-oxide-semiconductor transistors, wherein the body bias control circuitry is configured to supply body bias voltages to the body terminals of the p-channel metal-oxide-semiconductor transistors, and wherein the body bias control circuitry is configured to supply a reverse bias to the body bias terminal of the n-channel metal-oxide-semiconductor transistor of the second inverter during write operations into the memory cell.

2. The circuitry defined in claim 1, wherein the body bias control circuitry is configured to supply a forward bias to the body terminal of the address transistor during write operations into the memory cell.

3. The circuitry defined in claim 1, wherein the body bias control circuitry is configured to supply a reverse bias to the body bias terminal of the address transistor during read operations from the memory cell.

4. The integrated circuit defined in claim 1, wherein the body bias control circuitry is configured to dynamically control the body bias voltage supplied to the body terminal of the address transistor, is configured to dynamically control the body bias voltages supplied to the body terminals of the n-channel metal-oxide-semiconductor transistors, and is configured to dynamically control the body bias voltages supplied to the body terminals of the p-channel metal-oxide-semiconductor transistors.

5. The integrated circuit defined in claim 1, wherein the body bias control circuitry is configured to supply a reverse bias to the body bias terminal of the p-channel metal-oxide-semiconductor transistor of the second inverter during write operations into the memory cell.

6. The integrated circuit defined in claim 1, wherein the body bias control circuitry is configured to supply a forward bias to the body terminals of the address transistor, a reverse bias to the body terminals of the re-channel metal-oxide-semiconductor transistors, and a reverse bias to the body terminals of the p-channel metal-oxide-semiconductor during write operations into the memory cell.

7. Circuitry, comprising:

a memory cell comprising;

an address transistor with a body terminal; and

first and second cross-coupled inverters, each inverter having an n-channel metal-oxide-semiconductor transistor, a p-channel metal-oxide-semiconductor transistor, and an input and wherein the address transistor is coupled to the input of the first inverter, wherein each of the n-channel metal-oxide-semiconductor transistors has a respective body terminal, and wherein each of the p-channel metal-oxide semiconductor transistors has a respective body terminal; and

body bias control circuitry that is operable to supply a dynamic time-varying body bias voltage to the body terminal of the address transistor, is operable to supply dynamic time-varying body bias voltages to the body terminals of the n-channel metal-oxide-semiconductor transistors, and is operable to supply dynamic time-varying body bias voltages to the body terminals of the p-channel metal-oxide-semiconductor transistors, wherein the body bias control circuitry is configured to supply a forward bias to the body terminal of the address transistor, a forward bias to the body terminal of the p-channel metal oxide semiconductor transistor of the first inverter, a reverse bias to the body terminal of the n-channel metal-oxide-semiconductor transistor of the first inverter, a forward bias to the body terminal of the n-channel metal-oxide-semiconductor transistor of the second inverter, and a reverse bias to the body terminal of the p-channel metal-oxide-semiconductor transistor of the second inverter when writing a logic one into the memory cell.

8. The integrated circuit defined in claim 7, wherein the body bias control circuitry is configured to supply a forward bias to the body terminal of the address transistor, a reverse bias to the body terminal of the p-channel metal oxide semiconductor transistor of the first inverter, a forward bias to the body terminal of the n-channel metal-oxide-semiconductor transistor of the first inverter, a reverse bias to the body terminal of the n-channel metal-oxide-semiconductor transistor of the second inverter, and a forward bias to the body terminal of the p-channel metal-oxide-semiconductor transistor of the second inverter when writing a logic zero into the memory cell.

9. Circuitry, comprising:

a memory cell having an address transistor and having first and second cross-coupled inverters, each inverter having an n-channel metal-oxide-semiconductor transistor and a p-channel metal-oxide-semiconductor transistor, wherein the address transistor has a body terminal and wherein the address transistor is coupled to an input of the first inverter; and

body bias control circuitry that is operable to supply a dynamic time-varying body bias voltage to at least one of the transistors in the second inverter, wherein the body bias control circuitry is configured to supply a reverse body bias voltage to the n-channel metal-oxide-semiconductor transistor of the second inverter when writing data into the memory cell.

10. The circuitry defined in claim 9, wherein the body bias control circuitry is configured to supply a forward body bias voltage to at least one of the transistors in the second inverter when reading data from the memory cell.

11. An integrated circuit, comprising:

a memory cell having an address transistor and first and second cross-coupled inverters, each inverter having an input, an output, an n-channel metal-oxide-semiconductor transistor, and a p-channel metal-oxide-semiconductor transistor;

an address line connected to a gate in the address transistor, wherein the address transistor has a terminal coupled to the input of the first inverter and the output of the second inverter; and

body bias control circuitry that is operable to supply dynamic time-varying body bias voltages to a body terminal of the address transistor and is operable to supply dynamic time-varying body bias voltages to body terminals in the n-channel metal-oxide-semiconductor transistor and in the p-channel metal-oxide-semiconductor transistor in the second inverter, wherein the dynamic time-varying body bias voltages supplied to the body terminals in the n-channel metal-oxide-semiconductor transistor and in the p-channel metal-oxide-semiconductor transistor in the second inverter are different when writing a logic one into the memory cell than when writing a logic zero into the memory cell.

12. The integrated circuit defined in claim 11, wherein the body bias control circuitry comprises a multiplexer having a multiplexer output that is operable to supply a forward body bias voltage to the body terminal of the address transistor and a reverse body bias voltage to the body terminal of at least one of the transistors in the second inverter.

13. A method for performing read and write operations on a set of memory elements in an integrated circuit, comprising:

during a write operation, using body bias control circuitry to adjust memory element transistors in the memory elements to write strength settings; and

during a read operation, using the body bias control circuitry to adjust the memory element transistors in the memory elements to read strength settings, wherein the read strength settings are different from the write strength settings, wherein adjusting the memory element transistors to the write strength settings comprises weakening an n-channel metal-oxide-semiconductor transistor in cross-coupled inverters in the memory element.

14. The method defined in claim 13, wherein adjusting the memory element to the write strength settings comprises strengthening an address transistor in each memory element that is connected to cross-coupled inverters in that memory element.

15. A method for supplying body bias voltages to memory element transistors on an integrated circuit, wherein the memory elements transistors have associated speeds, comprising:

with test equipment, characterizing the associated speeds of memory element transistors on the integrated circuit to identify slow memory element transistors; and

during operation of the integrated circuit, supplying compensating body bias voltages to the slow memory element transistors to strengthen the slow memory element transistors, wherein the integrated circuit comprises a memory cell formed from cross-coupled inverters that include an re-channel metal-oxide semiconductor transistor; and

during write operations into the memory cell, weakening the n-channel metal-oxide semiconductor transistor.

16. The method defined in claim 15 wherein characterizing the speed of the memory element transistors comprises identifying fast memory element transistors, the method further comprising supplying compensating body bias voltages to the fast memory element transistors to weaken the fast memory element transistors.