United States Patent [i9]
Niimi et al.
[54] SEMICONDUCTOR MEMORY DEVICE HAVING SELF-REFRESH FUNCTION
[75] Inventors: Makoto Niimi; Shigemasa Ito, both of Kasugai; Toyonobu Yamada; Yoshihiro Takemae, both of Kawasaki; Yoshiharu Kato, Kasugai, all of Japan
[73] Assignees: Fujitsu Limited, Kawasaki; Fujitsu
VLSI Limited, Kasugai, both of Japan
[21] Appl. No.: 83,443
[22] Filed: Jun. 29,1993
[30] Foreign Application Priority Data
Jun. 29, 1992 [JP] Japan 4-170602
Jul. 9, 1992 [JP] Japan 4-182384
Aug. 7, 1992 [JP] Japan 4-211820
Sep. 21, 1992 [JP] Japan 4-251226
Jun. 18, 1993 [JP] Japan 5-147673
[51] Int. CI.6 G11C 7/00
[52] U.S. CI 365/222; 365/236
[58] Field of Search 365/222, 233.5,
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US005499213A [li] Patent Number: 5,499,213 [45] Date of Patent: Mar. 12,1996
[56] References Cited
U.S. PATENT DOCUMENTS
4,989,183 1/1991 Kumanoya 365/222
FOREIGN PATENT DOCUMENTS
3-149867 6/1991 Japan.
Primary Examiner—A. Zarabian
Attorney, Agent, or Firm—Staas & Halsey
[57] ABSTRACT
A semiconductor memory device has an oscillator unit for generating refresh pulses, a refresh address detection unit for detecting refreshed addresses and outputting a predetermined signal upon the completion of the refreshing of all addresses, and an output control unit for continuing a self-refresh mode to refresh all addresses according to the signal from the refresh address detection unit, before releasing the self-refresh mode in response to an external signal. Therefore, the refresh operation is continued until all cells are refreshed, thereby data stored in the semiconductor memory device is not lost and is correctly refreshed.
4 Claims, 41 Drawing Sheets
