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I have a MEMS microphone with an integrated PA. I'm going to use it as a trigger in a low-power device so I wanted to know if that internal PA is enough and I can connect it directly to the analog comparator of an ATtiny1626. I was going to use it like this:

Here are the specifications of the MEMS microphone:

  • Sensitivity: -42 db
  • Output impedance: 300 Ohms

The specifications of AC input of the ATtiny1626:

  • Input leakage current: 5 nA
  • Input offset: 2 +- 20 mV

schematic

simulate this circuit – Schematic created using CircuitLab

Is it possible to use it like this and have a few tens of millivolts to be detected by the AC unit considering enough audio pressure applied?

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2 Answers 2

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So is it possible to use it like this and have a few tens of millivolts to be detected by the AC unit considering enough audio pressure applied?

The microphone needs to be powered as per this diagram in the data sheet: -

enter image description here

So, you need to have a 2 volt nominal DC supply that powers the microphone. But, if you don't mind a small drop in sensitivity you can run the microphone from 1.6 volts to 3.6 volts: -

enter image description here

Then, making the assumption that the microphone sensitivity is -42 dbV (and not simply -42 dB), we can say that for a sound pressure level of 94 dB at 1 kHz, the microphone RMS output will be 7.94 mV or about 22 mV peak-to-peak.

I can't tell you if this is enough for your needs but, if there's any doubt, you could use a simple op-amp amplifier circuit to boost this by (say) ten times.

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The mic has a sensitivity of -42 dB, which more specifically means dB using 1V as reference. So it's similar to electret mics.

-42 dBV is 8 millivolts.

So it's not few tens of millivolts.

At considering what you mean by enough audio pressure applied, you get the 8 millivolts at an ear-deafening level of 94 dB SPL, usually measured with 1 meter distance between mic and the sound source.

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