Low-noise sigma-delta ADC

1 October 2008 Analogue, Mixed Signal, LSI

Analog Devices is enabling industrial equipment manufacturers to expand the operating speed and precision of sensitive measurement instruments with the introduction of a new sigma-delta ADC (analog-to-digital converter) which features an excellent combination of data rate and noise-free resolution. The 24-bit AD7190 achieves greater than true 16-bit noise-free resolution up to 2,4 kHz across all input voltages from 40 mV to 5 V.

The ADC includes an on-chip PGA (programmable-gain amplifier) with ultra­low-noise and drift from DC to 4,8 kHz. The design of the PGA allows the realisation of an ultra-low noise of only 7 nV rms at 4,7 Hz data rate with a gain of 128, and an offset drift of only 5 nV/°C. The AD7190 features an oscillator, temperature sensor, bridge power-down switch, reference detect monitor and a choice of single-ended, pseudo-differential or fully differential input channels.

Also included on-chip are simultaneous 50/60 Hz rejection, offset and gain calibration, open sensor detection, a choice of chopped or non-chopped signal, and four general-purpose output pins. A zero-latency mode is selectable in order to reduce software overheads if a valid conversion per data output is desired.

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