Semiconductor memory device with improved operation margin and increasing operation speed regardless of variations in semiconductor manufacturing processes

• US 6,741,505 B2
• Filed: 03/22/2002
• Issued: 05/25/2004
• Est. Priority Date: 09/27/2001
• Status: Expired due to Fees

• Current Assignee: Socionext Inc.
• Original Assignee: Fujitsu Limited
• Inventors: Yokozeki, Wataru
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Nguyen, Thinh T
• Application Number:
  US10/102,672
• Publication Number:
  US 20030063493A1
• Time in Patent Office: 795 Days
• Field of Search: 365/189.7, 365/210, 365/203, 365/207, 365/208, 365/174, 365/189
• US Class Current: 365/189.15
• CPC Class Codes: G11C 11/4094 Bit-line management or control circuits
• CPC Class Codes: G11C 11/4099 Dummy cell treatment; Reference voltage generators
• CPC Class Codes: G11C 2207/2281 Timing of a read operation
• CPC Class Codes: G11C 7/12 Bit line control circuits, e.g. drivers, boosters, pull-up circuits, pull-down circuits, precharging circuits, equalising circuits, for bit lines
• CPC Class Codes: G11C 7/14 Dummy cell management; Sense reference voltage generators

Abstract

A semiconductor memory device has a dummy bit line, a reference voltage generating circuit, a comparator circuit, and a timing signal generating circuit. The dummy bit line has a load equal to a load of a bit line, and the reference voltage generating circuit generates a reference voltage. The comparator circuit compares a potential of the dummy bit line with the reference voltage, and the timing signal generating circuit generates various kinds of timing signals based on an output of the comparator circuit. The semiconductor memory device simultaneously selects a plurality of dummy memory cells and connects the selected dummy memory cells to the dummy bit line, and adjusts the potential of the dummy bit line.

Claims

1. A semiconductor memory device comprising:

a dummy bit line having a load equal to a load of a bit line;

a reference voltage generating circuit generating a reference voltage;

a comparator circuit comparing a potential of said dummy bit line with the reference voltage; and

a timing signal generating circuit generating various kinds of timing signals based on an output of said comparator circuit, wherein

said semiconductor memory device simultaneously selects a plurality of dummy memory cells and connects the selected dummy memory cells to said dummy bit line, and adjusts the potential of said dummy bit line.

2. The semiconductor memory device as claimed in claim 1, wherein said dummy memory cells are a plurality of reading dummy memory cells that are driven by a dummy word line.

3. The semiconductor memory device as claimed in claim 2, wherein a plurality of load dummy memory cells are connected to said dummy word line.

4. The semiconductor memory device as claimed in claim 1, wherein a plurality of load dummy memory cells are connected to said dummy bit line.

5. The semiconductor memory device as claimed in claim 1, wherein the number of said dummy memory cells that are connected simultaneously is adjusted in a layout process.

6. The semiconductor memory device as claimed in claim 1, further comprising:

a switching circuit controlling the number of dummy memory cells that are connected simultaneously.

7. The semiconductor memory device as claimed in claim 1, further comprising:

a dummy memory cell selection signal generating circuit generating a dummy memory cell selection signal according to a dummy memory cell selection control signal; and

a dummy memory cell selecting circuit selecting a plurality of dummy memory cells that are connected simultaneously according to the dummy memory cell selection signal.

8. The semiconductor memory device as claimed in claim 7, wherein said dummy memory cell selecting circuit is formed as a switch having a reset function.

9. The semiconductor memory device as claimed in claim 1, wherein said comparator circuit is a current-mirror type differential amplifier.

10. The semiconductor memory device as claimed in claim 1, further comprising:

a comparator circuit output resetting circuit that resets an output of said comparator circuit when said comparator is inactive.

11. The semiconductor memory device as claimed in claim 1, further comprising:

a bit-line equalizing circuit that resets potentials of said bit lines and said dummy bit line to a predetermined voltage, wherein

said comparator circuit becomes inactive when said bit-line equalizing circuit is active, and said comparator circuit becomes active when said bit-line equalizing circuit is inactive.

12. The semiconductor memory device as claimed in claim 1, further comprising:

a dummy load capacitance provided in a wiring route from said bit-line equalizing circuit to said comparator circuit.

13. The semiconductor memory device as claimed in claim 1, further comprising:

a data bus equalizing circuit resetting potentials of data buses or dummy data buses to a predetermined voltage, wherein

said comparator circuit becomes inactive when said data bus equalizing circuit is active, and said comparator circuit becomes active when said data bus equalizing circuit is inactive.

14. The semiconductor memory device as claimed in claim 1, further comprising:

a sense amplifier reading a data of a memory cell that is connected to a predetermined word line; and

an output latch circuit latching an output of said sense amplifier.

15. The semiconductor memory device as claimed in claim 14, further comprising:

a dummy sense amplifier provided in a wiring route from said bit-line equalizing circuit to said comparator circuit, and simulating a load of said sense amplifier; and

a dummy output latch circuit simulating a load of said output latch circuit.

16. The semiconductor memory device as claimed in claim 1, further comprising:

a column switch selecting a predetermined bit line from among a plurality of bit lines, and connects the selected bit line to said sense amplifier, wherein

said column switch makes said dummy bit line simulate the loads of a plurality of bit lines to be selected.

17. A semiconductor memory device comprising:

a memory cell array including a plurality of word lines, a plurality of bit lines, and a plurality of memory cells each provided at an intersection point of said word line and said bit line;

a word driver driving a predetermined word line in said memory cell array according to an address signal;

a dummy bit line simulating said bit line;

a reference voltage generating circuit generating a reference voltage;

a comparator circuit comparing a potential of said dummy bit line with the reference voltage;

a timing signal generating circuit generating various kinds of timing signals based on an output of said comparator circuit; and

a plurality of dummy memory cells being simultaneously connectable to said dummy bit line.

18. The semiconductor memory device as claimed in claim 17, wherein said dummy memory cells are a plurality of reading dummy memory cells that are driven by a dummy word line.

19. The semiconductor memory device as claimed in claim 18, wherein a plurality of load dummy memory cells are connected to said dummy word line.

20. The semiconductor memory device as claimed in claim 17, wherein a plurality of load dummy memory cells are connected to said dummy bit line.

21. The semiconductor memory device as claimed in claim 17, wherein the number of said dummy memory cells that are connected simultaneously is adjusted on a layout.

22. The semiconductor memory device as claimed in claim 17, further comprising:

a switching circuit controlling the number of dummy memory cells that are connected simultaneously.

23. The semiconductor memory device as claimed in claim 17, further comprising:

a dummy memory cell selection signal generating circuit generating a dummy memory cell selection signal according to a dummy memory cell selection control signal; and

a dummy memory cell selecting circuit selecting a plurality of dummy memory cells that are connected simultaneously according to the dummy memory cell selection signal.

24. The semiconductor memory device as claimed in claim 23, wherein said dummy memory cell selecting circuit is formed as a switch having a reset function.

25. The semiconductor memory device as claimed in claim 17, wherein said comparator circuit is a current-mirror type differential amplifier.

26. The semiconductor memory device as claimed in claim 17, further comprising:

a comparator circuit output resetting circuit that resets an output of said comparator circuit when said comparator is inactive.

27. The semiconductor memory device as claimed in claim 17, further comprising:

a bit-line equalizing circuit that resets potentials of said bit lines and said dummy bit line to a predetermined voltage, wherein

said comparator circuit becomes inactive when said bit-line equalizing circuit is active, and said comparator circuit becomes active when said bit-line equalizing circuit is inactive.

28. The semiconductor memory device as claimed in claim 17, further comprising:

a dummy load capacitance provided in a wiring route from said bit-line equalizing circuit to said comparator circuit.

29. The semiconductor memory device as claimed in claim 17, further comprising:

a data bus equalizing circuit resetting potentials of data buses or dummy data buses to a predetermined voltage, wherein

said comparator circuit becomes inactive when said data bus equalizing circuit is active, and said comparator circuit becomes active when said data bus equalizing circuit is inactive.

30. The semiconductor memory device as claimed in claim 17, further comprising:

a sense amplifier reading a data of a memory cell that is connected to a predetermined word line; and

an output latch circuit latching an output of said sense amplifier.

31. The semiconductor memory device as claimed in claim 30, further comprising:

a dummy sense amplifier provided in a wiring route from said bit-line equalizing circuit to said comparator circuit, and simulating a load of said sense amplifier; and

a dummy output latch circuit simulating a load of said output latch circuit.

32. The semiconductor memory device as claimed in claim 17, further comprising:

a column switch selecting a predetermined bit line from among a plurality of bit lines, and connects the selected bit line to said sense amplifier, wherein

said column switch makes said dummy bit line simulate the loads of a plurality of bit lines to be selected.