Description

The AD7731 is a complete analog front-end for process controlapplications. The device has a proprietary programmable gainfront end that allows it to accept a range of input signal ranges,including low level signals, directly from a transducer. The sigma-deltaarchitecture of the part consists of an analog modulatorand a low pass programmable digital filter, allowing adjustmentof filter cutoff, output rate and settling time.The part features three buffered differential programmable gainanalog inputs (which can be configured as five pseudo-differentialinputs), as well as a differential reference input. The part operatesfrom a single +5 V supply and accepts seven unipolar analoginput ranges: 0 to +20 mV, +40 mV, +80 mV, +160 mV,+320 mV, +640 mV and +1.28 V, and seven bipolar ranges:±20 mV, ±40 mV, ±80 mV, ±160 mV, ±320 mV, ±640 mV and±1.28 V. The peak-to-peak resolution achievable directly fromthe part is 16 bits at an 800 Hz output rate. The part can switchbetween channels with 1 ms settling time and maintain a performancelevel of 13 bits of peak-to-peak resolution.The serial interface on the part can be configured for three-wireoperation and is compatible with microcontrollers and digitalsignal processors. The AD7731 contains self-calibration andsystem calibration options and features an offset drift of lessthan 5 nV/°C and a gain drift of less than 2 ppm/°C.The part is available in a 24-lead plastic DIP, a 24-lead SOICand 24-lead TSSOP package.APPLICATIONS Process Control PLCs/DCS Industrial Instrumentation