Can you hear me? I’m using a microphone on a 0.7mm2 MEMS die in a package measuring only 3.76mm x 4.72mm x 1.25mm. It’s the Akustica AKU230 digital, CMOS MEMS microphone, announced on March 30, 2010. For anyone who still doesn’t speak metric, the package size is less than 3/16” X 1/8” X 3/64.” For anyone still having trouble visualizing it, the package is smaller than a 14 point font capital “A” stamped out of a penny as a rectangle. In the simplest terms, really small.
Of course, I’m not really using the Akustica AKU230, but I could be. It is used primarily in notebook computers, just like the one I’m typing on.
The AKU230 is manufactured using conventional CMOS processes. The microphone membrane is a metal/dielectric layer, manufactured just like every other metal/dielectric layer in a CMOS process. The ADC circuitry is located around the membrane and is fabricated at the same time as the membrane during the same conventional CMOS processes. This approach offers savings in silicon area compared to a MEMS microphone fabricated using more traditional MEMS processes.
Some MEMS microphones have an analog audio output. Some have an analog audio output but can provide a digital output using a second semiconductor, essentially an ADC. Akustica MEMS microphones, including the AKU230, are the only MEMS microphones that combine the microphone and the ADC circuitry on one chip, offering a simpler, less expensive solution and one insertion cost rather than two.
In notebooks, the AKU230 eliminates audio signal interference from RF and EM noise sources, and provides a single wire stereo output for microphone arrays. Its small size makes it possible to place two microphones at the top of the notebook screen, an optimum location.
It’s time for design engineers to think outside their conventional boundaries. The Akustica AKU230 is a complete digital microphone in an unbelievably small package. So far, it’s been used primarily in notebooks; but, just for fun, imagine the possibilities for a digital MEMS microphone embedded in a button. More realistically, think about a digital MEMS microphone in a Bluetooth headset, on the wire leading to cell phone earbuds. There must be hundreds of applications. This microphone is small enough to spawn new applications in new products. All it takes is imagination.
Chief of Technology