Electronic Design

Low-Power Delta-Sigma ADC

Low-power delta-sigma ADC embedded systems requiring low-power analog functions can turn to the low-power ADS1244 24-bit, delta-sigma analog-to-digital converter (ADC). Developed by Texas Instruments' Burr-Brown division in Tucson, Ariz., this ADC is a third-order delta-sigma modulator and digital filter with a ±5-V differential input range.

The analog modulator measures the differential input signal against the differential reference. The reference is internally scaled so the input range is approximately twice the reference voltage. The digital filter simultaneously rejects both 50- and 60-Hz signals and sets the converter's frequency response. It completely settles in one cycle and outputs data at up to 15 samples per second. The ADS-1244 operates on 2.5- to 5.25-V analog supplies and 1.8- to 3.6-V digital supplies. It can be configured to operate on a single supply, but accuracy and resolution drop at the lower supply voltages.

A simple two-wire serial interface provides all of the necessary control. Self-calibration automatically operates at power-up and can be manually invoked at any time. Sleep mode reduces power consumption to less than 1 µW by shutting down all active circuitry. When only single conversions are needed, the ADS1244 can be placed into sleep mode while idle between measurements to further reduce the overall power dissipation. Multiple ADS1244s can be connected together to create a synchronously sampling multichannel measurement system.

Power is typically less than 270 µW in normal operation and less than 1 µW during sleep mode. A data sheet in PDF format is available at www-s.ti.com/sc/ds/ads1244.pdf. Samples are available immediately. In MSOP-10 packages, pricing is $2.95 in 1000-unit lots.

Texas Instruments
(800) 477-8924, ext. 4500

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