Linear Technology Corp. has introduced the LTC2943 multicell battery gas gauge that makes direct measurements of 3.6 V to 20 V battery stacks. Absolutely no level shifting circuitry on the supply and measurement pins is required to interface with multicell voltages, so total current consumption is minimized and measurement accuracy is preserved. The LTC2943 is a true high voltage gas gauge that measures charge, voltage, current and temperature to within 1 percent accuracy, all of the essential parameters required to accurately assess battery state of charge (SoC).
The LTC2943 is suited for multicell applications, including 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 bidirectional analog integrator accommodates either current polarity (battery charge or discharge), and a programmable prescaler allows for a wide range of battery capacities. Charge, voltage, current and temperature information are communicated to the host system over an I²C/SMBus-compatible 2-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.
The LTC2943 is offered in commercial and industrial versions, supporting operating temperature ranges from 0°C to 70°C and -40°C to 85°C, respectively. The LTC2943 is available in a RoHS compliant, 8-pin 3 mm by 3 mm DFN package. Pricing starts at $2.35 each in 1,000 piece quantities.