Dram refresh scheme with flexible frequency for active and standby mode

• US 20040141396A1
• Filed: 01/17/2003
• Published: 07/22/2004
• Est. Priority Date: 01/17/2003
• Status: Active Grant

• Current Assignee: Etron Technology Inc
• Original Assignee: Etron Technology Inc
• Inventors: Shiah, Chun, Ting, Tah-Kang Joseph, Liu, Shi Huei
• Granted Patent: US 6,894,917 B2
• Time in Patent Office: Days
• US Class Current: 365/222
• CPC Class Codes: G11C 11/406 Management or control of the refreshing or charge-regeneration cycles
• CPC Class Codes: G11C 11/40615 Internal triggering or timing of refresh, e.g. hidden refresh, self refresh, pseudo-SRAMs
• CPC Class Codes: G11C 2211/4061 Calibration or ate or cycle tuning
• CPC Class Codes: G11C 2211/4067 Refresh in standby or low power modes

Abstract

The present invention provides a method and an apparatus for DRAM refresh with different frequencies of refresh for active and standby mode. In addition, this invention utilizes different refresh frequencies during active and standby modes to optimize power dissipation and DRAM data integrity. The refresh frequency during active mode is higher than said refresh frequency during standby mode. The refresh frequency during active mode is higher than the prior art refresh frequency during active mode. The refresh frequency during standby mode is lower than the prior art refresh frequency during standby mode. The higher active mode refresh frequency allows the faster restoration of cell data, which is degraded by capacitive discharge coupling through the selection of adjacent word lines. The low standby mode refresh frequency provides a lower standby power dissipation which compensates for the higher active mode power dissipation caused by the higher active mode refresh frequency.

Claims

1. A method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode comprising the step of:

providing a higher refresh frequency for active mode than for standby mode.

2. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said refresh frequency during active mode is higher than prior art refresh frequency during said active mode.

3. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said refresh frequency during said standby mode is lower than said prior art refresh frequency during standby mode.

4. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said refresh frequency during active mode is higher than said refresh frequency during standby mode.

5. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said higher active mode refresh frequency allows faster restoration of cell data, which is degraded by capacitive discharge coupling through selection of an adjacent word line.

6. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said standby frequency can be lowered since cell charge lost due to adjacent word line switching does not occur.

7. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein during standby said word lines are not active.

8. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said higher refresh frequency during active mode causes active mode power dissipation to be greater than in prior art.

9. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said lower refresh frequency during standby mode causes standby mode power dissipation to be lower than in prior art.

10. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said higher power dissipation caused by said higher active mode refresh frequency is offset by said lower power dissipation due to said lower standby refresh frequency.

11. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein a count of word lines determines worse case cell degradation due to said capacitive coupling due to activity on said adjacent word lines.

12. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said worst case number of word lines determines said higher refresh frequency required during said active mode.

13. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein a flexible feature allows said refresh frequency of active mode to vary according to said word line counts.

14. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein a flexible feature allows said refresh frequency of standby mode to vary inversely according to said word line count so as to compensate for higher active mode power dissipation.

15. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said refresh frequency during standby mode is decreased more to compensate for said required increase of said refresh frequency during active mode to insure power dissipation is compensated adequately to meet required design specifications.

16. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein a sense amplifier is used to refresh said memory cells as needed during refresh time.

17. The method for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 1 wherein said refresh operation activate said word lines in a repeating ring order.

18. An apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode] comprising:

a refresh clock with higher frequency for active mode than for standby mode.

19. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said refresh frequency during active mode is higher than prior art refresh frequency during active mode.

20. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said refresh frequency during standby mode is lower than prior art refresh frequency during standby mode.

21. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said refresh frequency during active mode is higher than said refresh frequency during standby mode.

22. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said higher active mode refresh frequency allows faster restoration of cell data, which is degraded by capacitive discharge coupling through selection of an adjacent word line.

23. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said standby frequency can be lowered since cell charge lost due to adjacent word line switching does not occur.

24. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein during standby said word lines are not active.

25. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said higher refresh frequency during active mode causes active mode power dissipation to be greater than in prior art.

26. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said lower refresh frequency during standby mode causes standby mode power dissipation to be lower than in prior art.

27. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said higher power dissipation caused by higher active mode refresh frequency is offset by said lower power dissipation due to said lower standby refresh frequency.

28. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein a count of word lines determines worse case cell degradation due to said capacitive coupling due to activity on said adjacent word lines.

29. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said worst case number of word lines determines said higher refresh frequency required during said active mode.

30. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein a flexible feature allows said refresh frequency of active mode to vary according to said word line counts.

31. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein a flexible feature allows said refresh frequency of standby mode to vary inversely according to said word line count so as to compensate for higher active mode power dissipation.

32. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said refresh frequency during standby mode is decreased more to compensate for said required increase of said refresh frequency during active mode to insure power dissipation is compensated adequately to meet required design specifications.

33. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein a sense amplifier is used to refresh said memory cells ass needed during refresh time.

34. The apparatus for providing a dynamic random access memory, DRAM, refresh with flexible frequency for active and standby mode of claim 18 wherein said refresh operation activate said word lines in a repeating ring order.