MEMS microphones integrate interchip sound
R Colin Johnson
1/18/2011 12:48 AM EST
PORTLAND, Ore.—Analog Devices Inc. (ADI) aims to bring high-fidelity audio to industrial, business and consumer applications with the world's first micro-electro-mechanical system chip to package a MEMS microphone with an industry standard 24-bit data integrated interchip sound—I2S—interface.
"For industrial applications and for non-handset consumer devices, the key feature on the our new iMEMS mic is the I2S interface," said Kieran Harney, ADI's MEMS product line manager "For new designs, engineers can literally plug it straight into their signal processor, DSP or micro controller."
Handset manufactures have standardized on a pulse density modulated (PDM) encoding which is built into their main ASIC on their cell phones, allowing two microphones to be time multiplexed on a single data line using a single clock. However, non-handset consumer device designs are abandoning the PDM encoding in favor of I2C, which provides similar functionality, but uses pulse code modulation which is supported by standard microcontrollers and DSPs. Applications adopting I2S include surveillance cameras, IP Phones, video conferencing, Bluetooth headsets, game controllers, video cameras and other non-handset consumer applications.
The ADMP441 iMEMS microphone has an extended frequency response from 100 Hz to 15 kHz, a 61 dBA signal-to-noise ratio and 80 dBFS of power-supply-rejection along with ADI's patented dust filter, entire-package back-volume and high-quality audio signal processing. The one millimeter thick package measures 4.72 -by-3.76 millimeter in a reflow solder compatible surface mount package.
Analog Devices' 441 iMEMS digital microphone has a tiny silicon diaphram contained on a separate die measuring just one square millimeter.