PDM convert to analog

Question

Dear Sir or Madam, 
 
 in my studies I am working on a project to measure 2 microphones. 
 For this purpose a small sound absorber chamber is built to measure with measurement electronics an analog reference microphone (the b&k 4165) and a DUT (e.g. the digital microphone Infineon IM69D130-DS). 
 We used the 4165 mic as well as a suitable preamp and the FFT Analyzer 3160 from the company B&K. 
 The FFT Analyzer requires analog signals at the input and converts them to digital signals with a sampling rate of 131kHz. 
 My problem is to pick up the digital microphone IM69D130-DS. This MEMS micro gives as signal a 1-bit PDM signal, which I have to convert to an analog signal, so that the FFT Analyzer recognizes it. 
 Do you offer such an interface or chip that turns a PDM signal into an analog one? 
 
 kind regards

mthoren_adi · Accepted Answer

Indeed, if the FFT analyzer is targeted at audio applications, it may have a digital input. The Stanford Resarch SR1 has optical / TOSLINK inputs. I've never used them, but there are I2S to TOSLINK converters (do an internet search), and as noted above, PDM to I2S converters. 
 You will have to do some research and experimentation to see what will actually work, based on what your analyzer will accept. If it is ONLY analog, then yet another option would be to use PDM to I2S, capture the I2S data as an audio file (WAV or some compressed, lossless format), then finally, play back the file through a high-quality sound card to your analyzer. Compare the sound card specs to the expected microphone performance, to make sure that the sound card is NOT the limiting factor. 
 Again, we can only provide support for Analog Devices products, and if you have specific questions about the ADAU7002 (assuming that's useful to you), check the Engineer Zone Audio forum. 
 Good luck! 
 -Mark

Electronic Design Services - PartnerZone

PDM convert to analog

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