The LTC1392 is a micropower data acquisition system designed to measure temperature, on-chip supply voltage and a differential voltage. The differential inputs feature rail-to-rail common mode input voltage range. The LTC1392 contains a temperature sensor, a 10-bit A/D converter with sample-and-hold, a high accuracy bandgap reference and a 3-wire half-duplex serial interface. The LTC1392 can be programmed to measure ambient temperature, power supply voltage and an external voltage at the differential input pins, that can also be used for current measurement using an external sense resistor. When measuring temperature, the output code of the A/D converter is linearly proportional to the temperature in C. Production trimming achieves 2C initial accuracy at room temperature and 4C over the full 40C to 85C temperature range.