The AD7864 is a high speed, low power, 4-channel simultaneous sampling 12-bit A/D converter that operates from a single 5 V supply. The part contains a 1.65 ms successive approximation ADC, four track/hold amplifiers, a 2.5 V reference, an on-chip clock oscillator, signal conditioning circuitry, and a high speed parallel interface. The input signals on four channels are sampled simultaneously, thus preserving the relative phase information of the signals on the four analog inputs. The part accepts analog input ranges of 10 V, 5 V (AD7864-1), 0 V to +2.5 V, 0 V to +5 V (AD7864-2), and 2.5 V (AD7864-3). The part allows any subset of the four channels to be converted in order to maximize the throughput rate on the selected sequence. The channels to be converted can be selected via hardware (channel select input pins) or software (programming the channel select register).