MEMS microphone not working on my board

Community PCB Design
1

I am using the same MEMS microphone that Sparkfun uses in its MEMS microphone breakout board: https://www.sparkfun.com/products/9868

This is the MEMS microphone datasheet: http://www.invensense.com/wp-content/up … NMP401.pdf

For some reason I’m getting no AC output signal from the microphone on my own board. I attached the portion of my layout (highlighted to show the MEMS microphone circuit parts) and my schematic. There was no output from the amplifier, and then I checked the microphone output and there is only a 0.9VDC voltage with no AC signal. Does anyone have insight about why a MEMs microphone wouldn’t work?

Here’s my big question: why are there four GND points on the MEMS microphone? Are they all supposed to be connected to GND on the board even though they are already connected to each other on the component?

2

Component manufacturers seldom put multiple ground pads that don’t need connected.

If you look at the evaluation board document you will see that they use a ground pour to connect all the ground pads together.

So yes, all the ground pads should be connected together on your PCB.

Andy