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ADCs provide high-precision measurements for signal apps

Posted: 27 May 2008 ?? ?Print Version ?Bookmark and Share

Keywords:ADCs? precision measurements high? apps signal?

Texas Instruments Inc. (TI) has introduced two multichannel, 16bit, delta-sigma ADCs, which are believed to combine excellent DC accuracy and AC performance with cost-effective integration. The ADS1174 (4-channel) and ADS1178 (8-channel) provide a simultaneous-sampling measurement system for signal acquisition applications such as power metering, defibrillators and ECG monitors, as well as pressure sensors, coriolis flow meters and vibration/modal analysis.

The ADS1174 and ADS1178 feature 25kHz bandwidth, 2uV/C offset drift and up to 97dB SNR. Two operating modes allow for optimization of speed (52kSPS) or power dissipation (7mW/channel).

"Traditionally, industrial delta-sigma ADCs offering good drift performance use digital filters with large passband droop, resulting in limited signal bandwidth and suited for DC measurements," TI said. "High-resolution ADCs for audio applications offer larger usable bandwidths, but the offset and drift specifications are significantly worse (and often unspecified) than their industrial counterparts," added TI. The ADS1174 and ADS1178 combine these two types of converters, allowing for high-precision industrial measurements with excellent AC and DC specifications.

The high-order, chopper-stabilized modulator achieves very low drift and low noise over the signal bandwidth of DC up to the Nyquist frequency. The onboard decimation filter suppresses modulator and out-of-band noise, providing a usable signal bandwidth up to 90 percent of the Nyquist rate with stopband attenuation of 100dB.

A selectable SPI or frame sync serial interface allows for interfacing to DSPs, FPGAs and microcontrollers. Either interface supports daisy chaining to simplify readback of multiple ADS1174 or ADS1178 ADCs in high channel-count systems.

The ADCs are fully specified over the industrial temperature range of -40C to +105C. Available in identical packages, the ADCs are drop-in compatible with the high-performance, 24bit ADS1274 and ADS1278 for convenient upgrades. The ADCs are available now in HTQFP-64 PowerPAD packages.

- Gina Roos

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