Static information storage and retrieval – Powering – Data preservation
Patent
1995-12-20
1997-07-22
Popek, Joseph A.
Static information storage and retrieval
Powering
Data preservation
365228, G11C 1300
Patent
active
056509740
ABSTRACT:
A semiconductor device includes a first battery BAT 1; a second battery BAT 2; and switches SW1, SW2, SW3, and SW4. Switching block 13 is provided for switching a power source for backing up a memory 3 to retain data. Also a voltage comparator 5 is provided for comparing an external power supply voltage supplied by the power supply VCC of a host apparatus with a reference voltage Vref. In response to the signal from a main battery presence sensor block for sensing the presence of the first battery BAT 1 and the signal from the voltage comparator 5, the memory 3 is backed up to retain data by the external power supply voltage when it is supplied, and further, the second battery BAT 2 is charged by a charging circuit 6 driven by the external power supply voltage. When neither external power supply voltage nor first battery BAT 1 is present, the second battery BAT 2 backs up the memory 3 to retain data. Therefore, power consumption of both main and auxiliary batteries is lessened and memory backup is performed in an assured manner.
REFERENCES:
patent: 4451742 (1984-05-01), Aswell
patent: 5375246 (1994-12-01), Kimura et al.
patent: 5502682 (1996-03-01), Yoshimura
Mitsubishi Denki & Kabushiki Kaisha
Popek Joseph A.
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