Patent ID: 8078887

Claim:
A power supply voltage regulator circuit for supplying a primary power supply voltage or a secondary power supply voltage, which is lower than the primary power supply voltage, to a normal circuit and a backup system circuit having separate power supplies, the power supply voltage regulator circuit comprising: a power supply circuit that switches to a first, a second, a third, and a fourth state, and the switching is based on a combination of logic for a normal circuit power control signal for controlling power supplied to the normal circuit and a backup circuit power control signal for controlling power supplied to the backup system circuit; wherein in the first state when the normal circuit power control signal and the backup circuit power control signal are inactive, voltage is supplied to neither the normal circuit nor the backup system circuit, wherein in the second state when the normal circuit power control signal is active and the backup circuit power control signal is inactive, the primary power supply voltage is supplied to the normal circuit and the secondary power supply voltage is supplied to the backup system circuit, wherein in the third state when the normal circuit power control signal is inactive and the backup circuit power control signal is active, voltage is not supplied to the normal circuit and the secondary power supply voltage is supplied to the backup system circuit, and wherein in the fourth state when the normal circuit power control signal and the backup circuit power control signal are active, the primary power supply voltage is supplied to both the normal circuit and the backup system circuit.