Muxing MP34DT05-A signals with another component

[PKarn.1]

We are hooking up MP34DT05-A (showing SPK mic in the diagram) to GPIO pins of our processor configured for PDM clock and PDM data from the mic. The power supply to this mic is gated by an Enable signal from a GPIO from the same processor.

The mic is used infrequently, so we wish to mux the GPIO signals as signals to another component. The other component is enabled/disabled with an explicit Enable signal. When the other component is to be used, we wish to "turn off" the mic. MIC_EN is set low, gating off the power to the mic.

Question: When the Mic power supply is off, could the Mic still impact the AUD_CLK and AUD_DATA signals? One possible thought is if there is ESD protection internal to the Mic package. Essentially, we don't want the Mic to impact the Clock and Data signals if the power supply is zero.

I appreciate any help. Best Regards,

Prasad Karnik

[Eleon BORLINI]

Hi Prasad @PKarn.1​ ,

>> Question: When the Mic power supply is off, could the Mic still impact the AUD_CLK and AUD_DATA signals? One possible thought is if there is ESD protection internal to the Mic package. Essentially, we don't want the Mic to impact the Clock and Data signals if the power supply is zero.

The safest "switched-off" condition for a digital MEMS microphone such as the MP34DT05-A is Power supply OFF and AUD_CLK OFF, i.e. no clock coming from the application processor to the microphone (better if CLK pad of the mic is voltage controlled). However, if the mic is powered off (just Vdd OFF = 0V), it should not interfere with the clock and the data line (especially if the high level of the digital clock is low, for example 1.8V). I confirm that there are ESD cells internal to the package, but you should be careful in case an ESD (contact) discharge comes from the top package, since it might enter from the hole.

-Eleon