The MX844 is a fully integrated subsystem that measures temperature plus differential current and voltage. An internal temperature sensor measures ambient temperature with 2.5C accuracy. Current and voltage measurements are made differentially through a four input multiplexer connected to a programmable gain fully differential sense amplifier. The differential sense amplifier is optimized to measure very small positive or negative voltages near ground for low side bi-directional sensing. A dual slope ADC converts the temperature sensor or sense amplifier outputs to a 12-bit digital word that includes 3 digits plus sign. The input multiplexer channel and programmable gain amplifier range may be changed between ADC conversions. An on-chip voltage regulator enables the MX844 to operate over a wide input voltage range of 4.5 to 40 volts. Controller interrupt or over-voltage/over-current signals may be generated by a pair of 12-bit digital comparators configured as a window comparator or simple threshold detection function. The serial port supports standard 4-wire synchronous serial data, or asynchronous serial "talk-only" data, and is compatible with most 3.3V and 5V microcontrollers.