Static information storage and retrieval – Systems using particular element – Resistive
Reexamination Certificate
2008-09-09
2009-08-25
Ho, Hoai V (Department: 2827)
Static information storage and retrieval
Systems using particular element
Resistive
C365S210100, C365S222000
Reexamination Certificate
active
07580277
ABSTRACT:
Disclosed are a phase change memory with improved retention characteristic of a phase change device, and a method for refreshing the phase change memory. The fact that a memory is a DRAM interface compatible memory is exploited. There are provided dummy cells stressed in accordance with the number of times of read and write operations. Changes in the resistance value of the dummy cells are detected by comparator circuits. If the resistance value have been changed beyond a predetermined reference value (that is, changed to a low resistance), a refresh request circuit requests an internal circuit, not shown, to effect refreshing. The memory cells and the dummy cells are transitorily refreshed and correction is made for variations in the programmed resistance value of the phase change devices to assure the margin as well as to improve retention characteristic.
REFERENCES:
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patent: 2004-362761 (2004-12-01), None
Elpida Memory Inc.
Ho Hoai V
Sughrue & Mion, PLLC
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