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MEMS microphones Forum Discussions

JoakimWSI
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Hello Community

We are pondering  using the IM67D120A microphone in a project. This microphone can operate in one of four modes depending on the speed of the PDM clock, see the image attached.

However the MCU we are using only allows us to chose between three different frequencies: 1, 2 and 4 MHz. As you see, this would either put us above the allowed max frequency or between LPM & mode 3 or mode 3 & mode 2.

Our preference is to run the PDM clock at 2 MHz, but what behaviour can we expect from the mic when running at an intermediary clock speed? will the microphone glitch back and forth between two modes (and cause audible artifacts) or is the mode switching more seamless and nothing bad can be expected?

pdmclock.PNG

 

Best regards

J

1 Solution
Deepa_V
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Hi @JoakimWSI ,

The operating clock frequency of 1/2/4MHz lies inside the threshold of the switching frequencies. We cannot guarantee device operation/performance at Threshold frequency and it's possible that device is always switching between two modes. We do not recommend using IM67D120A at 2Mhz. If you cannot change the clock frequency on application side, we recommend using IM72D128, our high SNR microphone with IP57 environmental protection.
https://www.infineon.com/dgdl/Infineon-IM72D128-DataSheet-v01_01-EN.pdf?fileId=8ac78c8c80027ecd01806...

Best Regards,

Deepa

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Deepa_V
Moderator
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Moderator

Hi @JoakimWSI ,

The operating clock frequency of 1/2/4MHz lies inside the threshold of the switching frequencies. We cannot guarantee device operation/performance at Threshold frequency and it's possible that device is always switching between two modes. We do not recommend using IM67D120A at 2Mhz. If you cannot change the clock frequency on application side, we recommend using IM72D128, our high SNR microphone with IP57 environmental protection.
https://www.infineon.com/dgdl/Infineon-IM72D128-DataSheet-v01_01-EN.pdf?fileId=8ac78c8c80027ecd01806...

Best Regards,

Deepa

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JoakimWSI
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Hello Deepa!

Thanks for your very straight-forward and clear answer. Unfortunately, our design needs as high sensitivity as possible (we are not interested in loud sound, and want to capture quieter sounds with an as low noise flor as possible), and the 8 dB loss is less than optimal.

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Deepa_V
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Hi @JoakimWSI ,

If you can relax your 2MHz clock frequency requirement, you might find better available options to suit your application. You can possibly try for ones with ANC and higher SNR . Kindly go through options in the https://www.infineon.com/dgdl/Infineon-SensorSelectionGuide-ProductSelectionGuide-v01_00-EN.pdf?file...

Best regards,

Deepa

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