Small MEMS Microphone from Infineon with Excellent SNR and 520 A Power

Infineon combines outstanding audio quality and low lower in a compact microphone device using its own MEMS technology and intelligent ASIC architecture. Today's users of earpieces and audio-centric wearables have high expectations for sound quality and battery life.  Engineers must keep up with The Times and utilize advanced MEMS technology and innovative circuit design. To meet this demand, Infineon Technologies recently announced the launch of new members of its XENSIV MEMS microphone product line.  Known as IM69D128S, the microphone is a PDM (pulse density modulation) device designed to meet applications that require 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 is made up of a MEMS unit and an ASIC housed in a tiny module packaging. 

Focus on Size, Power, and Performance

Following Tyshchenko, the key technological trends driving MEMS microphones today are downsizing, reduced power consumption, and improved performance. Miniaturization is required to allow these devices to coexist with more sensors in 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 of this in mind, Tyshchenko states that the IM69D128S's digital microphone ASIC gives the maximum performance at nearly half the typical needed power consumption, at 520 A of power consumption and an SNR of 69 dB(A). Among the unique features of this new generation of Infineon MEMS microphones is "seamless power switching on microphone level," according to Tyshchenko. That is, it provides switching power modes with no audible distortions.

Sealed Dual Membrane MEMS Technology

The IM69D128S's MEMS are built with Infineon's latest proprietary sealed dual membrane MEMS technology. According to Tyshchenko, the SDM technique creates a sealed low-pressure hollow and a differential output signal by combining two membranes and a charged stator. "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.

Tyshchenko elaborates on the ASIC, stating that the digital ASIC ICD82 lies at the heart of the IM69D128S architecture.  The IC incorporates a charge pump, which is used to charge the stator.  A PGA (programmable gain amplifier) amplifies differential signals from two membranes to provide differential communication between the MEMS unit and the ASIC. “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.

The clock drives a power mode detector, and the flag pin toggles between several power modes. More information is available in the IM69D128S data sheet. According to Tyshchenko, this solution reduces power consumption by a factor of two while maintaining high SNR values—all contained within the same modular IC unit. True wireless earbuds, over-ear headsets, and hearing enhancement are all suitable for the IM69D128S. According to the corporation, it might potentially be used in other space-critical applications such as wearables, smartphones, and IoT devices.

All images used courtesy of Infineon Technologies

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