Miscellaneous active electrical nonlinear devices – circuits – and – Specific identifiable device – circuit – or system – With specific source of supply or bias voltage
Patent
1993-09-15
1995-01-17
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Specific identifiable device, circuit, or system
With specific source of supply or bias voltage
327530, 327546, 327 74, H02H 324, H02H 320
Patent
active
053828399
ABSTRACT:
An IC memory card used in a dual power supply voltage operation system and having a backup function is arranged to prevent destruction of data stored in an internal memory caused by an erroneous access in a non-operation-ensured voltage range between lower and higher operation-ensured voltage ranges. Three voltage levels divided from an external power supply voltage by voltage dividing resistors are compared with a reference voltage from a reference voltage generation circuit to determine whether the external power supply voltage is at the lower or upper limit of the lower operation-ensured voltage range or the lower limit of the higher operation-ensured voltage range. On the basis of outputs from these comparators, a memory protection signal generation circuit generates a memory protection signal to enable the memory to be protected even in the voltage range between the lower and higher operation-ensured voltage ranges.
REFERENCES:
patent: 4288865 (1981-09-01), Graham
patent: 4428020 (1984-01-01), Blanchard, Jr.
patent: 4451742 (1984-05-01), Aswell
patent: 4639681 (1987-01-01), Hasegawa
patent: 4907183 (1990-03-01), Tanaka
patent: 5140183 (1992-08-01), Takenaka
Callahan Timothy P.
Le Dinh
Mitsubishi Denki & Kabushiki Kaisha
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