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ICS-40300 MEMS Microphone @ 1-30Hz

ripper121

Hello image,

I search for a Microphone which can detect low freq in infra sound range.

I found the ICS-40300 which has a range from 6Hz.

 

Can you help me please to set up a OPamp with filter for 1-30Hz?

I need to connect it to a 12Bit ADC @ 3.3V.

 

With best regards

 

Stefan

  • Try the Texas Instruments website.

    They have an online OpAmp design app that helps you get the right parts.

     

    DAB

  • How much have you done so far?

     

    The product page has links to application notes that show how to amplify the output, using an op-amp, for feeding to a codec.

    https://www.invensense.com/products/analog/ics-40300-3/

     

    If you only have 12-bits for the ADC, it won't cover the whole range of the microphone (microphone 99dB, ADC 72dB approx), so you need to make a decision as to where you place the ADC relative to the microphone (ie how much gain you have). Are you are interested in the loud end of the range (the maximum 130dB that they quote is VERY loud), where you'd just need enough gain to bring the output level of the sensor up to the input range of the A/D (a gain of 5 or 6, by the looks of things) or the quiet end of the range where you might need a gain of several hundred.

     

    This isn't really my area of expertise, but I'd say you'd find it easier if you get the gain in there first and then consider the filtering as a second step after that.

     

    For the filter, you need to tell us more about what the filtering is trying to achieve. How quickly does it need to diminish the signal outside the passband? Should a signal at 300Hz (a decade above your high cut-off point) be reduced by a factor of ten? A hundred? A thousand? Does it matter if there is variation of the signal level within the passband or should it be as flat as possible? [The microphone response isn't level over that range anyway, so maybe that question is a bit moot.] How much do phase changes of different frequencies in the passband matter? If you're dealing with sound that might not matter, but if this is really a form of instrumentation and you're looking at waveshape then it would.

     

    Random thoughts:
    You might find it better to work with a lower ADC reference voltage than 3.3V.
    Do you need the low cut-off at 1Hz from the active filter (ie does it need to be a band-pass filter) or can the coupling capacitor do that sufficiently for you (so the op-amp filter is just a low-pass filter)?
    Are you going to try and power this from the processor supply?
    Is it going to be a single supply?