Analog Devices Inc. AD7710AN

Description
The AD7710 is a complete analog front end for low-frequency measurement applications. It accepts low-level signals directly from a strain gage or transducer and outputs a serial digital word. It employs a sigma-delta conversion technique to realize up to 24 bits of no missing codes performance. The input signal is applied to a proprietary programmable gain front end based around an analog modulator. The modulator output is processed by an on-chip digital filter. The first notch of this digital filter can be programmed via the on-chip control register, allowing adjustment of the filter cutoff and settling time.
The part features two differential analog inputs and a differential reference input. Typically, one of the channels will be used as the main channel with the second channel used as an auxiliary input to measure a second voltage periodically. It can be operated from a single supply (by tying the Vss pin to AGND), provided that the input signals on the analog inputs are more positive than -30 mV. By taking the Vss pin negative, the part can convert signals down to -Vap on its inputs. The AD7710 thus performs all signal conditioning and conversion for a single- or dual-channel system.
The AD7710 is ideal for use in smart, microcontroller-based systems. Input channel selection, gain settings, and signal polarity can be configured in software using the bidirectional serial port. The AD7710 contains self-calibration, system calibration, and background calibration options, and also allows the user to read and write the on-chip calibration registers.

Features
Charge-balancing ADC
24 bits, no missing codes
±0.0015% nonlinearity
Gains from 1 to 128
2-channel programmable gain front end
Differential inputs
Low-pass filter with programmable filter cutoffs
Bidirectional microcontroller serial interface
Ability to read/write calibration coefficients
Internal/external reference option
Single- or dual-supply operation
Low power (25 mW typ) with power-down mode (7 mW typ)

Applications
Weigh scales
Thermocouples
Process control
Smart transmitters
Chromatography