Low power real-time clock circuit having system and battery powe

Details Low power real-time clock circuit having system and battery powe Low power real-time clock circuit having system and battery powe

1996-11-22

1998-11-17

Callahan, Tim

Miscellaneous active electrical nonlinear devices, circuits, and

Specific signal discriminating without subsequent control

By presence or absence pulse detection

327 63, 327 68, 327 70, H03K 524

Patent

active

058381716

ABSTRACT:
A circuit for power arbitration, low battery voltage detection, and the operation of battery backed circuitry for systems in which the system power supply voltage range overlaps that of a battery source. A voltage regulator is used to regulate the battery voltage so that the voltage range of the battery source is below the voltage range of the system supply. The regulator is based on a silicon-bandgap referenced methodology and consumes an insignificant amount of current so that the battery life is not appreciably affected. The regulator also has a smaller variation in its output voltage than the battery. A temperature and supply voltage compensated voltage is produced by the combination of a subthreshold current source, parasitic bipolar devices, and voltage buffering, and used to provide a voltage source for the battery backed circuitry of the system. The regulated voltage is set to a value lower than the system supply and serves as the battery supply input for the power arbitration circuitry. The regulated voltage permits the internal power arbitration scheme of the present invention to be equivalent to existing arbitration circuits even though the battery and system supply voltage ranges overlap.

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Vittoz, E.A., et al. "A Low-Voltage CMOS Bandgap Reference," pp. 573-577, IEEE Journal of Solid-State Circuits, vol. SC-14, No. 3, Jun. 1979.
Tzanatias, G. et al., "A CMOS Bandgap Voltage Reference," pp. 655-657, IEEE Journal of Solid-State Circuits, vol. SC-14, No. 3, Jun. 1979.

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