AD7864

The AD7864 is a high speed, low power, 4-channel simultaneous sampling 12-bit A/D converter that operates from a single +5V supply. The part contains a 1.65 m s successive approximation ADC, four track/hold amplifiers, 2.5 V reference, 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 10V, 5 V (AD7864-1), 0 V to 2.5 V, 0 V to 5 V for AD7864-2 and 2.5V (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 either hardware (channel select input pins) or software (programming the channel select register).

A single conversion start signal (CONVST) simultaneously places all the track/holds into hold and initiates 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 means of a 12-bit para llel data bus using the standard CS and RD signals. Maximum through-put 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 thro ughput rate for the read after conversion sequence operation will depend on the read cycle time of the processor. See Timing and Control section.

The AD7864 is available in a small (0.3 sq. inch area) 44-lead MQFP.