Akustica, the company that introduced the first digital single-chip microphone, is introducing its fourth-generation fully-integrated AKU230 complementary metal-oxide semiconductor (CMOS) digital microphone on a 0.7-mm2 single-chip die, the world’s smallest. This tiny die includes an acoustic transducer, a pre-amplifier, and a sigma-delta (∑-Δ) modulator. Other digital micro electro-mechanical systems (MEMS) microphones on the market have a total silicon area of 1.5 mm2(see the figure).
“This is our first product announcement since Bosch acquired us and represents our efforts in answering the growing market need for improved voice quality in noisy notebook computer environments. It enables the movement of microphones to laptop displays,” explained Eric Bauer, Akustica’s product marketing manager.
“Our CMOS digital microphones are part of a technology evolution toward higher-quality and more-uniform voice microphones that are made on a reliable and robust CMOS process. They’ve been tested to 1000 hours of reliability levels,” said Davin Yuknis, Akustica’s sales and marketing manager.
The single-chip microphone uses a membrane that is less than 400 µm, compared to other digital MEMS microphone chips that use membranes greater than 500 µm and electret condenser microphones (ECMs) that use 4000-µm membranes, to enable the large chip design shrink. This shrink is less than one-half the silicon area used by other MEMS microphones.
The top-ported surface-mountable microphone uses pulse density modulation, which produces a single-bit digital output stream, enabling the multiplexing of stereo microphone data onto a single wire and supporting dual-microphone setups. The chip features a 56-dB typical signal-to-noise ratio (SNR), a frequency range of 50 Hz to 22 kHz, -26-dBS typical sensitivity, 10% maximum total harmonic distortion, and -57 dBFS typical power supply rejection. Part-to-phase matching is within ±10% maximum, and no-load current consumption is 1.2 mA maximum (11 µA typical) at a supply of 5.5 V.
Because of its digital nature, the AKU230 is virtually immune to all forms of radio frequency interference (RFI) and electromagnetic interference (EMI). This allows it to be integrated on a platform regardless of proximity to displays, Wi-Fi antennae, or other sources of interference that would degrade the signal of conventional analog microphones.
The product is available in an industry standard 3.76-by-4.72-by 1.2-mm package in form, fit, and function. It is footprint-compatible with Akustica’s earlier version AKU2002 family. The AKU230 is presently designed into and is aimed at microphone arrays, slate PCs, notebook computers, tablets, ultra-mobile PCs, mobile internet devices, webcams, and camera modules.
The AKU230 is in mass production and is priced at $1.30 each in 10,000-unit quantities. It is available in a land-grid array (LGA) package.