Wolfson launches first MEMS microphone product

EDN Europe, 20 Oct 2008

Wolfson Microelectronics has announced the first of an intended series of analogue MEMS (micro-electro-mechanical systems) silicon microphones. Key points of the WM7110 and WM7120 are small size and high signal to noise ratio (SNR) for consumer applications requiring low power consumption and signal quality. The devices use a membrane technology, constructed on a standard CMOS process, that Wolfson has developed following its acquisition in January 2007 of Oligon. The company calls it new line AudioPlus True Mics technology. Wolfson is also offering enhanced WM7110E and WM7120E versions of the two devices, which are the first MEMS silicon microphones to deliver a sensitivity tolerance of +/-1dB.
The WM7110 (4.72 x 3.76 x 1.25mm package size) and ultra compact WM7120 (3.76 x 2.95 x 1.10mm package size) devices typically consume 160µA making them suitable for portable applications. Both devices offer 62dB SNR (A-weighted), reducing the noise floor in the microphone, THD (total harmonic distortion) of 0.5% maximum at 100dB SPL, good linearity and flat phase response.
As the first MEMS silicon microphones to offer a tighter sensitivity tolerance of +/-1dB, the enhanced WM7110E and WM7120E devices change the rules for multiple microphone design and bring innovative new applications into cost effective reach. As well as removing the need for costly production line testing and calibration software algorithms, the tighter +/-1dB sensitivity tolerance give the microphones better matching - a crucial element in the design of microphone arrays for beam-steering. Noise cancellation design can also be substantially improved, the company says, by using more closely-matched microphones.
WM7110 and WM7110E will be available for sampling in November 2008 and the WM7120 and WM7120E will be available in December. The WM7110 and WM7120 cost $1.64 each (1000).