Akustica debuts tiny single-chip MEMS microphone

Pittsburgh, Pa. — Akustica, Inc. has unveiled the AKU230 single-chip digital micro-electromechanical systems (MEMS) microphone, aimed at high-quality voice applications in laptops, tablets and netbook PCs. This is the first Akustica CMOS MEMS microphone manufactured by the company since it was acquired by Bosch in 2009.

The genesis came about with the increasing popularity of voice over Internet applications such as Skype, said Eric Bauer, product marketing manager for Akustica. “As consumers use those devices more, they demanded higher voice quality similar to what they were getting in phone conversations.”

“The problem with this came from the use of traditional analog microphones and how it was designed within the laptop computer. A laptop is a very noisy environment for a microphone. You have mechanical noise from the keyboard, cooling fan, spinning hard disk, and speakers, and on top of that you have a lot of electrical and RF noise from the various antennas — WiFi, Bluetooth, and 3G,” explained Bauer.

“What the AKU230, as a digital MEMS microphone, has allowed laptop designers to do is integrate the microphone as far away from those mechanical noise sources as possible and integrate it, for instance, on a camera module, located at the very top of the laptop screen along the bezel,” said Bauer. “And because it’s a digital microphone the output signal is immune to those RF and electromagnetic interferences sources from various antenna so it significantly lowers the overall noise of the system and improves voice quality,” he added.

The AKU230 offers highly-matched sensitivity control and stereo-microphone data multiplexing, targeting dual microphone arrays that create directionality and noise suppression to enhance audio quality. Key specs include -26 dBFS +/-2dB sensitivity, 56 dB typical SNR, and -57 dBFS power supply rejection.

Inventor of the first single-chip digital MEMS microphone

Akustica is the inventor of the first single-chip digital MEMS microphone. “We developed the world’s first and still the only single-chip MEMS microphone,” said Davin Yuknis, manager of marketing and sales, Akustica. “We did this in 2006 and continue to build on this platform. It was one of the main reasons Bosch acquired us in 2009.”

With a footprint of 3.76 x 4.72 mm, and 1.25 mm tall, the AKU230 package is also 30 percent thinner than the previous generation of digital microphones, and is well suited to thin form-factor integrations. It can easily fit inside the bezels of the smallest tablet computers, said Akustica.
Akustica believes the new AKU230 — the company’s fourth generation of digital MEMS — is the industry’s smallest fully-integrated MEMS device. The company has shrunk the size of the monolithic AKU230 die, which contains the microphone membrane, amplifier and sigma-delta converter, to 0.84 x 0.84 mm.
Leveraging Bosch’s design expertise, quality, and high-volume production has allowed Akustica to develop the world’s smallest MEMS device, said Bauer. “If you pop off the top of the package you’ll see just the single chip, not a two-chip solution like most traditional MEMS microphones.”

“It’s only .84 mm per side or 0.7-mm square so it’s a significant die shrink not only from our first product introduction but historically through the four different generations of products,” said Bauer.

In addition, the packaged part is designed to meet an industry-standard form, fit and function, said Bauer. “One of our customers’ requirements is dual supply so we’re able to provide that with this package, and by making it within this size and industry-standard specification, it’s also very easy for our customers to integrate,” said Bauer.

The AKU230, Akustica’s 4th-generation MEMS microphone, leverages Bosch’s MEMS fabrication capabilities and global supply chain. The CMOS MEMS microphone is produced at Bosch’s foundry in Reutlingen, Germany.

Akustica has always maintained an in-house MEMS, ASIC, and package design team, and now as part of Bosch, has added in-house foundry capabilities. Akustica says this combination “enables a new level of MEMS innovation that allows the company to rapidly develop both tailored solutions for customers and compelling features for new products.”

The main business of the foundry is manufacturing MEMS devices and it has a zero ppm quality defect level, which is ingrained into every product that goes through that fab, said Yuknis.

The AKU230 is in mass production and is priced at $1.30 in quantities of 10,000. Available in a LGA package, the AKU230 is designed for high-volume assembly into camera modules, microphone arrays, and other consumer electronic platforms.