Thomas D. Petty

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 1 V BiCMOS rail-to-rail amplifier with n-channel depletion-mode input-stage

This amplifier is fabricated on a SMARTMOS/sup TM/ flow with depletion-mode nMOS, vertical p-n-p, and high-frequency n-p-n transistors. Most techniques for achieving rail-to-rail input stage performance concentrate on the use of complementary bipolar or enhancement MOSFET devices to allow the amplifier common-mode range to include both supply rails. These techniques require a minimum supply voltage of 1.8 V for bipolar and 3 V for CMOS to allow a transition from sensing common mode voltages at ground when the p-n-p or pMOS pair is active, to sensing common-mode voltages at the positive supply when the n-p-n or nMOS pair is active. This amplifier uses a single pair of depletion-mode nMOS devices to allow low-voltage, rail-to-rail operation.

A quad low voltage rail-to-rail operational amplifier

A low-voltage rail-to-rail amplifier that has a NPN PNP switchable differential input stage allowing rail-to-rail input voltage swings is presented. The inputs can be overdriven without causing phase reversal in the output signal. The amplifier provides rail-to-rail output voltage swings which extend to within 50 mV of either rail. The output stage is current boosted to provide up to 50 mA of drive current.<<ETX>>

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/.

Sleep-mode amplifier

A novel technique for designing micropower operational amplifiers is described. An amplifier that operates in two separate states-sleep-mode and awake mode-is presented. Although the amplifier draws only 40 mu A of drain current while operating in the sleep-mode, it is able to drive 50 mA of output current when it transitions to the awake-mode. Transition between the two states is automatic, depending on the output current driving requirement.<<ETX>>