The AD7864 is a high speed， low power， 4-channel， simultaneous sampling 12-bit analog-to-digital converter （ADC） that operates from a single 5 V supply. The part contains a 1.65 μs successive approximation ADC， four track-and-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 sample simultaneously 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）。 Any subset of the four channels can be converted to maximize the throughput rate on the selected sequence. Select the channels to convert via hardware （channel select input pins） or software （programming the channel select register）。 A single conversion start signal （CONVST） simultaneously places all the track-and-holds into hold and initiates a conversion sequence for the selected channels. The EOC signal indicates the end of each individual conversion in the selected conversion sequence. The BUSY signal indicates the end of the conversion sequence. Data is read from the part by a 12-bit parallel data bus using the standard CS and RD signals. Maximum throughput for a single channel is 500 kSPS. For all four channels， the maximum throughput is 130 kSPS for the read-during-conversion sequence operation. The throughput rate for the read-after-conversion sequence operation depends on the read cycle time of the processor. See the section. The AD7864 is available in a small （0.3 square inch area） 44-lead MQFP.