The AD7811 and AD7812 are high speed, low power, 10-bit A/D converters that operate from a single +2.7 V to +5.5 V supply. The devices contain a 2.3 s successive approximation A/D converter, an on-chip track/hold amplifier, a 2.5 V on-chip reference and a high speed serial interface that is compatible with the serial interfaces of most DSPs (Digital Signal Processors) and microcontrollers. The user also has the option of using an external reference by connecting it to the VREF pin and setting the EXTREF bit in the control register. The VREF pin may be tied to VDD. At slower throughput rates the power-down mode may be used to automatically power down between conversions.