Method and apparatus for distinguishing momentary loss of battery contact from an undervoltage condition
First Claim
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1. A circuit for distinguishing momentary loss of battery contact from a battery undervoltage condition in a portable device, comprising:
- an undervoltage sensing circuit that senses a battery voltage provided at a battery contact of the portable device and compares it to an undervoltage reference voltage level corresponding to an undervoltage limit and provides an undervoltage signal to a controller of the portable device when the battery voltage falls below the undervoltage limit;
a current sensing circuit that senses current into the portable device from the battery, and provides a low current signal while the current is below a current threshold; and
a reference adjustment circuit that compares the low current signal with a power on flag provided by the controller of the portable device indicating the portable device is powered on, wherein the reference adjustment circuit lowers the undervoltage reference voltage level to a reduced value only while the low current signal indicates the current is below the current threshold and the power on flag indicates the portable device is powered on.
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Abstract
A method and apparatus for distinguishing momentary loss of battery contact from a battery undervoltage condition in a portable device sense the current into the portable device from the battery, and when the current drops to a level indicating that contact with the battery has been lost, the portable device is allowed to operate at a lower voltage than a nominal undervoltage limit of the battery until contact is resumed.
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Citations
20 Claims
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1. A circuit for distinguishing momentary loss of battery contact from a battery undervoltage condition in a portable device, comprising:
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an undervoltage sensing circuit that senses a battery voltage provided at a battery contact of the portable device and compares it to an undervoltage reference voltage level corresponding to an undervoltage limit and provides an undervoltage signal to a controller of the portable device when the battery voltage falls below the undervoltage limit; a current sensing circuit that senses current into the portable device from the battery, and provides a low current signal while the current is below a current threshold; and a reference adjustment circuit that compares the low current signal with a power on flag provided by the controller of the portable device indicating the portable device is powered on, wherein the reference adjustment circuit lowers the undervoltage reference voltage level to a reduced value only while the low current signal indicates the current is below the current threshold and the power on flag indicates the portable device is powered on. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A method for distinguishing a momentary loss of battery contact from a battery undervoltage condition in a portable device, comprising:
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comparing a voltage level at a battery contact with an undervoltage reference voltage level corresponding to an undervoltage limit, and providing an undervoltage signal when the battery voltage falls below the undervoltage limit; detecting a current passing through the battery contact and providing a low current signal when the current is below a current threshold; lowering the undervoltage reference voltage level to a reduced value only while the low current signal indicates the current is below the current threshold and a power on flag provided by a controller of the portable device indicates the portable device is powered on; and when the undervoltage reference voltage level is lowered, operating at least a portion of the portable device, including the controller, from a bulk capacitor coupled in parallel with the portion of the portable device, and maintaining the power on flag. - View Dependent Claims (11, 12, 13, 14, 15, 16)
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17. A portable device that is powered by battery that provides voltage and current via at least one battery contact, comprising:
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a hardware section including a controller; a current sense element connected in series between the battery contact and the hardware section; a bulk capacitor having first and second terminals, with one terminal coupled in parallel with the hardware section; a current sense comparator that senses a current through the current sense element and provides a low current signal while the current is below a current threshold; an undervoltage sensing circuit that senses a battery voltage provided at the battery contact of the portable device and compares it to an undervoltage reference voltage level that corresponds to an undervoltage limit and provides an undervoltage signal to the controller when the battery voltage falls below the undervoltage limit; and a reference adjustment circuit that compares the low current signal with a power on flag provided by the controller that indicates the portable device is powered on, wherein the reference adjustment circuit lowers the undervoltage reference voltage level to a reduced value only while the low current signal indicates the current is below the current threshold and the power on flag indicates the portable device is powered on. - View Dependent Claims (18, 19, 20)
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Specification