The AD7870/AD7875/AD7876 is a fast, complete, 12-bit A/D converter. It consists of a track/hold amplifier, 8 s successiveapproximation ADC, 3 V buried Zener reference and versatile interface logic. The ADC features a self-contained internal clock which is laser trimmed to guarantee accurate control of conversion time. No external clock timing components are required; the on-chip clock may he overridden by an external clock if required.