Infineon Unveils Tiny MEMS Microphone Touting High SNR, 520 μA Power

Today’s users of hearables and audio-centric wearables have high expectations when it comes to both sound quality and battery life. Engineers have to keep pace leveraging advanced MEMS technology and innovative circuit designs.

Feeding such needs, Infineon Technologies recently announced a new member of its XENSIV MEMS microphone product family. Dubbed the IM69D128S, the microphone is a PDM (pulse density modulation) device aimed at applications that need a mix of high signal-to-noise ratio (SNR), low microphone self-noise, long battery life, and high reliability, according to the company.

 

The XENSIV IM69D128S MEMS microphone comprises a MEMS unit and an ASIC in a tiny module package.

 

The microphone module consists of a MEMS and an ASIC combined in a tiny 3.5 mm × 2.65 mm × 0.98 mm package. In this article we analyze the key specs of the IM69D128S, and share input from our chat with Anastasiia Tyshchenko, Product Manager for Consumer Sensors at Infineon.

 

Focus on Size, Power, and Performance

According to Tyshchenko, the important technology trends driving MEMS microphones these days are miniaturization, shrinking power consumption, and boosting performance. Miniaturization is necessary to enable these devices to fit in along with more sensors within existing applications.

Reduced power consumption is needed to prolong the life of battery-dependent, wireless products, she says. Meanwhile, the performance aspect applies to multiple application spaces. “Increased performance means studio quality sound expectations for the consumer domain,” says Tyshchenko. “There’s also exploration of new use cases in medical and industrial branches.”

With all that in mind, Tyshchenko says that, at 520 μA of power consumption and an SNR of 69 dB(A), the IM69D128S’s digital microphone ASIC offers what the company claims is the highest performance with almost half of the average required power consumption.

Among the new aspects this new generation of Infineon’s MEMS microphones provide is what Tyshchenko refers to as “seamless power switching on microphone level.” That means it offers switching power modes without any hearable artifacts.

 

Sealed Dual Membrane MEMS Technology

The MEMS portion of the IM69D128S is built using Infineon’s latest proprietary sealed dual membrane MEMS technology. Tyshchenko says that the SDM approach uses two membranes and a charged stator to create a sealed low-pressure cavity and a differential output signal.

“The architecture enables ultra-high SNR, very low distortions, and enables high ingress protection (IP57) against water and dust at a microphone level,” she says.

 

M69D128S uses Infineon’s proprietary sealed dual membrane MEMS technology. It employs two membranes and a charged stator to create a sealed low-pressure cavity and a differential output signal.

 

This MEMS architecture is also what allows high performance in a small package, while the IM69D128S’s ASIC provides reduced power consumption and seamless switching functionality.

 

Digital ASIC Optimizes for High SNR and Low Power

Getting into more detail on the ASIC, Tyshchenko says that the digital ASIC ICD82 is the core of the IM69D128S’s design. The IC embeds a charge pump that is used to charge the stator. Differential connectivity between the MEMS unit and the ASIC is enabled via a PGA (programmable gain amplifier) that amplifies differential signals from two membranes. “Those signals are forwarded to the power-optimized 4-bit sigma-delta ADC,” says Tyshchenko.

 

“There are dual supply voltages—for the analog and digital parts—which is what allows us to reduce power consumption and noise.”

 

The digital ASIC ICD82 is the heart of the IM69D128S’s design. Its architecture achieves high SNR while keeping power consumption low.

 

A power mode detector is controlled by the clock, while the flag pin is used to switch between different power modes. More information is available in the IM69D128S data sheet.

According to Tyshchenko, this design allows the power consumption to be reduced by a factor of two, while still achieving the high SNR values—all contained within the same modular IC unit.

Hearable devices well suited for the IM69D128S include true wireless earbuds, over-ear headsets, and hearing enhancement. But it also could be applied to other space-critical applications such as wearables, smartphones, and IoT devices, according to the company.

Infineon says that its IM69D128S PDM microphone is available and can be ordered now.

 

All images used courtesy of Infineon Technologies