Static RAM with optimized timing of driving control signal for sense amplifier

• US 6,556,472 B2
• Filed: 01/08/2002
• Issued: 04/29/2003
• Est. Priority Date: 06/12/2001
• Status: Expired due to Term

• Current Assignee: Socionext Inc.
• Original Assignee: Fujitsu Limited
• Inventors: Yokozeki, Wataru
• Primary Examiner(s): Hoang, Huan
• Application Number:
  US10/038,827
• Publication Number:
  US 20020186579A1
• Time in Patent Office: 476 Days
• Field of Search: 365/154, 365/156, 365/210
• US Class Current: 365/154
• CPC Class Codes: G11C 11/419 Read-write [R-W] circuits
• CPC Class Codes: G11C 7/06 Sense amplifiers; Associated circuits , e.g. timing or triggering circuits

Abstract

The present invention is a static RAM comprising a memory cell array having memory cells located at intersections of word lines and bit lines, and a sense amplifier for amplifying a voltage of the bit lines; this static RAM further comprising: dummy memory cells selected when the word line is selected; a dummy bit line connected to the dummy memory cells; a timing signal generating circuit for generating a timing control signal in response to a change in potential of the dummy bit line; and a dummy memory cell selecting circuit for, in response to a selection of a word line in a word line group including a plurality of the word lines, selecting the dummy memory cell shared by the word line group.

Claims

1. A static RAM comprising:

a memory cell array having memory cells located at intersections of word lines and bit lines;

a sense amplifier for amplifying a voltage of said bit lines;

dummy memory cells selected when said word line is selected;

a dummy bit line connected to the dummy memory cells;

a timing signal generating circuit for generating a timing control signal in response to a change in potential of said dummy bit line; and

a dummy memory cell selecting circuit for inputting a word line group including a plurality of said word lines and selecting said dummy memory cell shared by the word line group in response to a selection of at least one of the word lines in said word line group.

2. The static RAM, according to claim 1, wherein a clock is supplied from outside and an address is supplied in synchronization with said clock.

3. The static RAM, according to claim 1, wherein said timing control signal includes a sense amplifier enable signal for enabling said sense amplifier.

4. The static RAM, according to claim 1, wherein said dummy memory cells are provided at the same pitch as the memory cells in the memory cell array;

a dummy cell unit is composed of a plurality of the dummy memory cells; and

said dummy memory cell selecting circuit selects a plurality of dummy memory cells in said dummy cell unit at the same time.

5. The static RAM, according to claim 4, wherein said dummy memory cells are located along dummy bit line and the plurality of dummy memory cells in said dummy cell unit are selected at the same time so as to drive the dummy bit line in parallel.

6. The static RAM, according to claim 1 or 4, wherein each of said dummy memory cells each comprises a latch circuit having two cross-connected inverters, and one of a pair of nodes in the latch circuits are connected to a high level or low level power source.

7. The static RAM, according to claim 1, wherein said memory cell array has a plurality of word line groups;

and a dummy memory cell selecting circuit and dummy cell unit are provided for each of said word line groups.

8. The static RAM, according to claim 7, wherein the plurality of dummy memory cells in said dummy cell unit are selected at the same time and drive the dummy bit line in parallel.

9. The static RAM, according to claim 1, wherein a dummy cell unit setting circuit is provided between said dummy memory cell selecting circuit and said dummy memory cells, for variably setting the number of dummy memory cells belonging to said dummy cell unit.

10. The static RAM, according to claim 9, wherein said dummy cell unit setting circuit comprises:

a switch group for propagating or not propagating a dummy memory cell selecting signal output by said dummy memory cell selecting circuit to said dummy memory cells; and

a switch setting circuit for placing part or all of said switch group in a propagating state.

11. A static RAM comprising:

a memory cell array having memory cells located at intersections of word lines and bit lines;

a sense amplifier for amplifying a voltage of said bit lines in response to a sense amplifier enable signal;

a plurality of dummy memory cells aligned with said memory cell array and disposed in the direction of the bit lines;

a dummy bit line connected in parallel to the plurality of dummy memory cells;

a timing signal generating circuit for generating said sense amplifier enable signal in response to a change in potential of said dummy bit line; and

a dummy memory cell selecting circuit for selecting a plurality of the dummy memory cells in response to the selection of said word line.

12. The static RAM, according to claim 11, wherein a clock is supplied from outside, an address is supplied in synchronization with said clock, and the operation cycle is controlled by said clock.

13. The static RAM, according to claim 11, wherein the word lines in said memory cell array are divided into word line groups each including a plurality of word lines, and said dummy memory cell selecting circuit is provided for each of the word line groups.

14. The static RAM, according to claim 13, wherein a dummy cell unit is composed of a plurality of the dummy memory cells selected at the same time;

said dummy cell unit is provided for each of said word line groups; and

said dummy cell unit is selected by said dummy memory cell selecting circuit.

15. The static RAM, according to claim 11, wherein each of said dummy memory cells comprises a latch circuit having two cross-connected inverters, and one of a pair of nodes in the latch circuits are connected to a high level or low level power source.