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ADMP521 mems microphone modulation levels

Question asked by dhonig@universal on Oct 1, 2012
Latest reply on Oct 1, 2012 by dhonig@universal

I am trying to drive a 521 using SPI hardware to drive the PDM clock (1Mhz) and capture pulses.

(Yes this is a hack but its been done before, see http://www.cypress.com/?app=forum&id=2232&rID=43249)

I can see variable PDM data come in when I clock the IC (and after its woken up).

 

When I drove a 521 and then LPF'ed the data pulses using a 10Khz filter, I could see the waveform with a 'scope, but only 180mV peak to peak.

 

Is this normal operation?   Why, with a very loud tone, don't I see more amplitude?  Shouldn't we get lots of FFF.FF and 000...00 sequences that represent full-scale measurements?

 

Thanks

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