MEMS digitizes microphone market

ORLANDO, Fla. — High-end laptop computers are switching from analog to digital microphones based on microelectromechanical systems, according to Akustica Inc. (Pittsburgh), which announced its first design win Monday (May 22).

Fujitsu's LifeBook Q2010 will include two AKU2000 single-chip microphones located on the display's bezel, according to Akustica. Davin Yuknis, vice president of marketing at Akustica, said the company has “other design wins pending.”

Akustica also announced the AKU2001, a chip model that permits multiple microphones to share a single interface wire.

Codec maker SigmaTel Inc. (Austin, Texas) simultaneously announced AKU2001 support that permits designs to multiplex microphones on a single interface wire with no additional circuitry.

The silicon microphone market reached nearly 100 million units last year and will grow to 800 million units by 2010, according to market watcher Yole Development (Lyon, France). Most are analog chip microphones made for analog cell phones by Knowles Electronics (Itasca, Ill.) and Sonion MEMS A/S (Roskilde, Denmark).

Akustica, by contrast, says its approach simplifies system design by including the diaphragm, analog preamplifier and analog-to-digital conversion functions on a single CMOS chip to facilitate integration with digital devices, such as the expanding number of voice-over-Internet-protocol (VoIP) ports. The tiny MEMS diaphragm is fabricated on a standard CMOS wafer along with all supporting circuitry. The diaphragm is freed to move by a second step that etches away sacrificial material below and around it.

SigmaTel, for its part, unveiled a family of four-channel high-definition audio codec chips. SigmaTel's new STAC9205 and STAC9255 codecs can handle two AKU2001 microphones on a single interface wire. The four-channel codecs allow two-channel VoIP to run simultaneously with other two-channel stereo audio applications.

The on-chip interface is said to allow notebook manufacturers to handle two-channel, high-definition audio or integrate up to four digital microphones for future stereo signal localization and noise canceling algorithms built into Microsoft's forthcoming Vista operating system.