High-Performance MEMS Microphone

With the increasing demand for high-quality microphones for consumer devices, the trend is toward MEMS-type microphones that offer high SNR or signal-to-noise ratio and low THD or total harmonic distortion. Apart from this, the microphones must also exhibit a wide dynamic range and a high AOP or acoustic overload point.

The MEMS microphone IM69D130, from Infineon, meets the above requirements superbly. Infineon has designed its microphone to provide low self-noise or high SNR of 69 dB(A), lower than 1% THD at 128 dBSPL, and an AOP of 130 dB SPL.

IM69D130 has a tight sensitivity of 36±1 dB and a phase tolerance of ±2°. With a low-frequency roll-off of 28Hz, the microphone offers a wide dynamic range of 105 dB. The current consumption of the microphone is only 980 µA, while in low-power mode, it consumes only 300 µA.

Infineon has used its patented Dual Backplate MEMS technology for making this microphone. This has given the IM69D130 microphone a miniaturized symmetrical design similar to that of studio condenser microphones. The design offers high linearity of signal output within a wide dynamic range of 105 dB. Even when the sound pressure levels reach 128 dB SPL, the microphone output has a distortion well below 1%. Infineon’s tight manufacturing tolerances result in a flat frequency response reaching as low as 28 Hz and a very close phase matching between microphones. This is a very important factor for applications using multi-microphone arrays.

The electronics associated with the microphone consist of an ASIC along with an amplifier featuring extremely low noise. There is also a high-performing sigma-delta ADC to convert the analog signal from the microphone to a digital signal. The user can select different power modes to suit specific requirements of current consumption.

Infineon trims each IMD69D130 microphone in production with IFX, their advanced calibration algorithm. This not only results in sensitivity tolerances as low as ±1 dB but also matches the phase response tightly to ±2° between microphones. This is very important for applications requiring beamforming support.

Infineon has designed their IMD69D130 microphones as extremely low-latency digital microphones. Their aim for these microphones is to use them in applications that require active noise cancellation, and where the microphone must process the audio data rather quickly.

The IMD69D130 microphones deliver the best-in-class group delay performances. This allows the benefits of digital microphones to system designs that had to rely on analog microphones up until now. The physical size of these microphones is only 4.00 x 3.00 x 1.20 mm.

There are some key benefits of using IMD69D130 microphones. They offer excellent far-field and soft audio signal pick-up. The output signal from these microphones is clear even when the sound pressure levels are very high. Moreover, these microphones enable the precise steering of audio beams for applications requiring advanced audio algorithms.

Typical applications of these digital MEMS microphones include systems with VUI or voice user interfaces such as IoT devices, home automation, and smart speaker systems. Headphones and earphones benefit from the excellent ANC or active noise cancellation offered by these microphones. Conference systems, camcorders, and cameras benefit from the high-quality audio these microphones capture.