We are using SSM2019 for balanced MIC pre-amp. It is powered by +/- 15v source.
Occassionaly a device fails in operation with no apparent reason. When testing failed device with multi-meter it looks like the input stage broke but I can't be sure on that.
The design include schottky diodes (BAR43CFILM) for clamping the input signals. In addition the microphone input connector has ESD protection diodes (TPD2E007).
I moved your question to the Audio community. Someone here should be able to assist you.
Usually, failures of this type are the result of EOS (electrical over stress) damage. Does the failure appear immediately after assembly, or does it happen after it has been in use for some time? Have you swapped ICs and retested the board?
Would it be possible for you to share your schematic with me? I would like to review your ESD protection scheme. I would be happy to start a private discussion if you are not comfortable posting your design in this public forum.
Here is the relevant part of the schematics.
It looks like you are doing some rigorous ESD and EMC protection. I am curious about the connection between CH_GND and GND_ANALOG_AUDIO. Do you have other isolated ground nets in the design? I generally recommend that designs have only one single ground with one single solid ground plane.
With regards to the units that have failed, did they fail in service or after assembly? Do they all appear to fail in the same way? Have you removed the IC off the board to confirm that the broken input that you describe is in the SSM2019 and not in one of the passives on the board?