CMOS low battery voltage detector
First Claim
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1. A detector for providing a low battery voltage indication comprising:
- a stable voltage reference and comparator circuit for comparing the battery voltage and the voltage reference;
a switch means to switch between a first operational state and a second operational state;
a switched capacitor circuit to store charges related to the battery voltage and the reference voltage in each operational state; and
a clock to initiate switching between the first and second states;
wherein an output from the comparator during the second state indicates whether the battery voltage is below a preset threshold (Vmin) such that
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Abstract
A system and method for detecting a low battery voltage supplied to a battery operated integrated circuit. A stable reference voltage provided by a bangap reference is compared with the battery voltage. A switched capacitor circuit is used instead of the more conventional resistor combination to supply a scaled representation of the battery voltage. Power requirements are reduced by combining the bandgap reference and the comparator into a single component.
16 Citations
14 Claims
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1. A detector for providing a low battery voltage indication comprising:
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a stable voltage reference and comparator circuit for comparing the battery voltage and the voltage reference;
a switch means to switch between a first operational state and a second operational state;
a switched capacitor circuit to store charges related to the battery voltage and the reference voltage in each operational state; and
a clock to initiate switching between the first and second states;
wherein an output from the comparator during the second state indicates whether the battery voltage is below a preset threshold (Vmin) such that - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A detector for providing a low battery voltage indication comprising:
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a stable voltage reference and comparator circuit for comparing the battery voltage and the voltage reference;
switch means to switch between a first operational state and a second operational state;
a switched capacitor circuit to store charges related to the battery voltage and the reference voltage in each operational state; and
a clock to initiate switching between the first and second states;
wherein an output from the comparator during the second state indicates whether the battery voltage is below a preset threshold (Vmin) set such that;
- View Dependent Claims (11)
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12. A method of detecting low battery voltage supplied to an integrated circuit comprising:
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providing a stable voltage reference and comparator circuit for comparing battery voltage against the reference voltage;
providing a capacitor circuit for storage charges associated with the battery voltage and the reference voltage;
providing switching means to switch between a first phase wherein said capacitors are charged to a first voltage level and a second phase wherein said capacitors are charged to a second level; and
comparing said first and second levels to determine whether said battery voltage is above or below a preset threshold (Vmin) such that - View Dependent Claims (13, 14)
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Specification