24-Bit, 8-/16-Channel, 250 kSPS, Sigma-Delta ADC with True Rail-to-Rail Buffers

The AD7175-8 is a low noise, fast settling, multiplexed, 8-/16- channel (fully/pseudo differential) Σ-Δ analog-to-digital converter (ADC) for low bandwidth inputs. It has a maximum channel scan rate of 50 kSPS (20 µs) for fully settled data. The output data rates range from 5 SPS to 250 kSPS.

The AD7175-8 integrates key analog and digital signal condition-ing blocks to allow users to configure an individual setup for each analog input channel in use. Each feature can be user selected on a per channel basis. Integrated true rail-to-rail buffers on the analog inputs and external reference inputs provide easy to drive high impedance inputs. The precision 2.5 V low drift (2 ppm/°C) band gap internal reference (with output reference buffer) adds embedded functionality to reduce external component count.

The digital filter allows simultaneous 50 Hz and 60 Hz rejection at a 27.27 SPS output data rate. The user can switch between different filter options according to the demands of each channel in the application. The ADC automatically switches through each selected channel. Further digital processing functions include offset and gain calibration registers, configurable on a per channel basis.

The device operates with a 5 V AVDD1 . AVSS supply, or with ±2.5 V AVDD1/AVSS, and 2.5 V to 5 V AVDD2 and IOVDD supplies. The specified operating temperature range is .40°C to +105°C. The AD7175-8 is available in a 40-lead LFCSP package.

APPLICATIONS

* Process control: PLC/DCS modules

Temperature and pressure measurement

* Medical and scientific multichannel instrumentation

* Chromatography

* Fast and flexible output rate: 5 SPS to 250 kSPS

* Performance specifications

17.2 noise free bits at 250 kSPS

20.2 noise free bits at 2.5 kSPS

24 noise free bits at 20 SPS

INL: ±1 ppm of FSR

* 85 dB filter rejection of 50 Hz and 60 Hz with 50 ms settling

* 85 dB filter rejection of 50 Hz and 60 Hz with 50 ms settling

* User configurable input channels

8 fully differential channels or 16 single-ended channels

Crosspoint multiplexer