The ADAU1977 has a built-in Microphone input and Mic Bias circuit. I have a redundant inputinto my system to two ADAU1977s. I have a single microphone that needs toconnect to one input on each ADAU1977. How can I connect the singlemicrophone to the two ADAU1977s robustly so that if one of the ADAU1977 dies orshorts the mic inputs the other ADAU1977 will still operate correctly with themicrophone?
Due to impedance issues I would not try to drive two microphone inputs with one microphone. I think the best way is to use two microphones. I do not know what microphones you are using or the amount of space you have. The MEMS microphones are quite small so I would look for even more redundancy by having two microphones.
I am assuming you are using the microphone circuit as per the datasheet with the electret microphone which can support the recommended bias circuit. If that is the case then, connecting single microphone to two inputs can be wired to work with some redundancy.
So if you plan to do it then connect the microphone bias resistors as usual but add 2k to 4kohm resistors in series to each of the inputs to ADAU1977 from microphone terminals. Please remember this is valid only for the microphone biased as shown in the application circuit of the datasheet.