ADMP401 connection

Hello,

I have moved this discussion from the Intertial MEMS community to the Audio community. We will answer questions about MEMS microphones in this forum, while the internal MEMS forum is focused on devices like accelerometers and gyroscopes.

Do you have one of the ADMP401 evaluation boards? The ADMP401 is available on both a flex pcb (EVAL-ADMP401Z-FLEX), on which the power, ground, and output signals are brought out on wires, or a rigid pcb (EVAL-ADMP401Z), which is battery-powered and the audio signal is output on a mono 3.5 mm mini-jack.You can find user guides for these here: http://www.analog.com/en/evaluation/eval-mic-all/eb.html.

You can connect the audio output from either of these to the microphone input on your PC, although you should consider that a PC's audio input is typically low-quality and will likely be lower-performance (noisier) than the microphone itself. If you are capturing voice with the microphone, then you probably will want to add some gain to the signal. The ADMP401 has a sensitivity of -42 dBV, which means that with a 94 dB SPL input signal, its output will be 7.9 mV rms. Typical speech levels are about 60-70 dB SPL, so it's common to add some gain to the analog signal before the ADC (before recording it). You might want to start with 10-20 dB of gain, and work your way up from there. Your ultimate goal should be to maximize the signal level you're recording without clipping the ADC.

One example of a preamp stage used with a MEMS microphone is available in one of our Circuits from the Lab: http://www.analog.com/en/circuits-from-the-lab/CN0262/vc.html. This shows an ADMP504 analog microphone connected to the SSM2167 preamp IC.