Battery gas gauge operates up to 20V

The LTC2943 from Linear Technology is a multi cell gas gauge designed to make direct measurements of 3.6 to 20V battery stacks.

According to the company, the device requires no level shifting circuitry on the supply and measurement pins to interface with multi cell voltages, enabling total current consumption to be minimised and measurement accuracy to be preserved. The LTC2943 is a true high voltage gas gauge that measures charge, voltage, current and temperature to within 1% accuracy. It is best suited to applications such as professional power tools and portable medical equipment. Battery current is measured by monitoring the voltage across an external, high side sense resistor and integrating this information to infer charge. A bi-directional analogue integrator accommodates either current polarity (battery charge or discharge), and a programmable pre-scaler allows for a range of battery capacities. Charge, voltage, current and temperature information are communicated to the host system over an I²C/SMBus-compatible two-wire interface that is also used to configure the gas gauge. The host can program high and low thresholds for all measured parameters, which if tripped, signal an alert using either the SMBus alert protocol or by setting a register flag.