ICs To Squeeze Preamp And ADC Into Electret MICs

By combining digital modulation and gain functions into a tiny low-cost IC, designers at National Semiconductor Corp. made it possible to deliver a digitized audio output from electret condenser microphones (ECMs).

The new ICs will replace the low-level analog outputs common to conventional ECMs with more robust digital signals that have greater immunity to noise and RF interference. Other expected benefits include simplified partitioning of baseband functions and lower overall system cost for some applications.

This technology will integrate a preamp with a sigma-delta (ΣΔ) analog-to-digital converter (ADC) (see the figure). Customized IC products based on this technology are expected to be released by the end of the year.

For more information, see "Digital Microphones, Applications and System Partitioning," available at http://edge.national.com.

For more on digital voice technology, visit the National Semiconductor Web site at www.national.com/see/mic or call (800) 272-9959.