Thanks to digital voice technology, electret condenser microphones (ECM) now come with built-in high-performance amplifiers for high-fidelity sound quality in handsets and other portable wireless applications. Using its mixed-signal VIP10 process, National Semiconductor has readied two amplifiers, the LMV1024 and LMV1026, which incorporate digital modulation techniques to offer improved sound quality, while reducing overall system cost and form factor.

“With mixed-signal capability so small that it fits inside existing ECMs, National Semiconductor's LMV1024 and LMV1026 amplifiers integrate digital voice directly inside microphones, providing 20 kHz CD-quality stereo sound, never before achieved in these form factors,” said Erroll Dietz, vice president of National Semiconductor's amplifier products group. “By integrating the sigma-delta codec, the amplifier, regulator, and several filter components inside the existing 6 mm ECM, National Semiconductor reduces the size of the overall solution and provides simplified system design for the customer.”

Integrating digital output at the microphone is the second step in National Semiconductor's strategy of enabling the world's first four-wire ECM with built-in gain and sigma-delta modulation to deliver the best possible audio fidelity. Applications that are using this technology are microphones in mobile handsets, PDAs and other portable, wireless applications.

According to the developer, these next-generation microphone amplifiers produce an oversampled single bit stream that connects directly to a DSP in a digital audio system. These amplifiers allow the user the flexibility of adjusting clock frequency ranging between 1 MHz to 3.25 MHz.

The LMV1024 and LMV1026 are designed for very robust signal-to-noise ratio (SNR) and acoustic audio sensing and eliminate sensitive, low-level analog signals from the output of the ECM. Plus, by integrating external components inside the microphone, it simplifies the system design routing and layout.

Unveiled at the recent CTIA show in New Orleans, La, the LMV1024 and LMV1026 are offered in six-bump micro SMD packages.

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