Troy L. Stockstad

Circuit and method of monitoring battery cells

A battery monitoring circuit (10) sequentially samples individual voltages across a string of serially coupled battery cells (12-18). A control circuit (32) controls first and second multiplexers (34,42) to sample each battery voltage for an over-voltage condition. A comparator (52) detects an over-voltage condition by comparing a divided down battery voltage against a reference. The conduction path through the battery cells is disabled upon detecting a fault condition by a transistor (26) in the battery cell conduction path. The battery cells are further sequentially sampled for an under-voltage fault. The comparator detects an under-voltage condition by comparing a second divided down battery voltage against the reference. The conduction path through the battery cells is disabled upon detecting a fault condition by a transistor (24) in the battery cell conduction path.

A micropower safety IC for rechargeable lithium batteries

A rechargeable lithium battery safety IC designed for monitoring cell voltage and current in the battery is presented. The circuitry is capable of protecting batteries of one to four series connected cells via a programmable circuit architecture with a cell voltage limit accuracy of +/-1%. The circuitry has an average current drain of 25 /spl mu/A. The Li safety IC with integrated series FETs has an area of 18.4 mm/sup 2/.