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ChRegBrg
Visitor II
August 17, 2023
Solved

IMP23ABSU Ultrasonic MEMS Microphone (analog) - Is there a digital alternative

  • August 17, 2023
  • 2 replies
  • 2021 views

Hello,

the STEVAL-MIC007V1 with the IMP23ABSU is on the first sight quiet interesting with the microphone bandwith up to 80kHz. However (due to imprecise reading from me) it turned out that this is a analog MEMS microphone. The STEVAL-MIC001V1 with the MP34DT05-A on the other hand is a digital MEMS microphone which puts out a PDM signal, which is in my opinion/application more suitable. But the 80kHz Bandwidth is more interesting toward industrial applications, but when using the STM32L496 the maximum frequency for the ADC is 80MHz and I would need 160MHz to sample the signal without aliasing. My question is: Is there an alternative digital MEMS microphone with 80kHz bandwidth with PDM output (STEVAL?) or is there a "easy" preprocessing implementation for the IMP23ABSU (also with minimal external electronic)?

Best regards,

ChRegBrg

    This topic has been closed for replies.
    Best answer by niccolò

    Hi @ChRegBrg ,

    for the ultrasound application that was developed for the STWIN.box the sampling frequency is 192kHz, and there is just a simple amplifier between microphone and microcontroller, so the STM32U5 ADC is able to process at this speed =)

    If this answers your question, please, mark this as "best answer", by clicking on the "accept as solution" to help the other users of the community

    Niccolò

    2 replies

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    Peter BENSCH
    Technical Moderator
    August 17, 2023

    Well, there is a reason why analogue MEMS microphones have such a wide bandwidth: digital MEMS microphones already have built-in signal pre-processing and the AD converter, which together can be considered a low-pass filter.

    For this reason, digital MEMS microphones are only suitable for the audible audio range, while analogue MEMS microphones reach into the ultrasonic range, which is particularly interesting in industry for e.g. predictive maintenance, despite higher external expenditure (opamps, possibly filters, analogue processing, etc).

    Does this answer your question?

    Regards
    /Peter

    C
    ChRegBrgAuthor
    Visitor II
    August 17, 2023

    Hello Peter,

    tank you for your quick answer! Yes you partly answered my question. However lets say i want to use the MEMS microphone with 80MHz (for predictive maintenance), is there an ST Controller with and ADC which is capable sampling with 160kHz, or would you suggest preprocessing the signal externally? On the STWin.box (STEVAL-STWBXCS1) there is if i am not wrong also an IMP23ABSU. Is the signal here processed completely programatically or is there also external electronic used? 

    Best regards,

    ChRegBrg

    N
    niccolòAnswer
    ST Employee
    August 21, 2023

    Hi @ChRegBrg ,

    for the ultrasound application that was developed for the STWIN.box the sampling frequency is 192kHz, and there is just a simple amplifier between microphone and microcontroller, so the STM32U5 ADC is able to process at this speed =)

    If this answers your question, please, mark this as "best answer", by clicking on the "accept as solution" to help the other users of the community

    Niccolò

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