Static information storage and retrieval – Read/write circuit – Testing
Patent
1998-02-19
1999-12-14
Mai, Son
Static information storage and retrieval
Read/write circuit
Testing
365190, 365202, G11C 700
Patent
active
060026227
ABSTRACT:
A margin test on a Dynamic Random Access Memory (DRAM) in accordance with the invention begins with a supply voltage level being stored in all memory cells of the DRAM. Circuitry incorporated into each sense amplifier of the DRAM then isolates the digit line equilibrating circuitry in each sense amplifier from the cell plate voltage DVC2 or supply voltage V.sub.cc to which the equilibrating circuitry is normally connected and connects the equilibrating circuitry to ground instead. The equilibrating circuitry is then activated for a predetermined refresh interval of about 150 to 200 milliseconds to equilibrate the true and complementary digit lines in each digit line pair of the DRAM to ground for the refresh interval. This stresses all the memory cells in the DRAM with a V.sub.cc -to-ground voltage drop for the entire refresh interval. The DRAM is then restored to normal operations and all the memory cells in the DRAM are read to identify any that leaked too much charge during the refresh interval, which identifies any memory cells that failed the margin test and require repair.
REFERENCES:
patent: 5208778 (1993-05-01), Kumanoya
patent: 5265056 (1993-11-01), Butler
patent: 5500824 (1996-03-01), Fink
patent: 5544108 (1996-08-01), Thomann
patent: 5610867 (1997-03-01), Debrosse
Mai Son
Micro)n Technology, Inc.
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