ADAU1787 ADC Protection Diodes

Hello VS,

OK, I will try my best to give you a helpful answer. We do not have a circuit that we have fully tested and can say this is the way to do it. So there is a disclaimer for this post. You need to investigate to see if this will work on your system and that the specs on the part will work to protect the IC.

Yes, 5V will really kill the ADC if the current is high enough. If you have huge resistors keeping the current low that helps but every time I ask our IC layout design engineers they always say you cannot count on the internal clamps to protect the chip for high currents and frequent voltages that are too high. It is for fast ESD events and that is all.

I have seen many designs where they used Schottky diode clamps and I have used them in my personal designs as well. The BAT54SLT1G is one I recently used. There are MANY flavors of these sorts of parts but it did seem to work well to keep the larger currents from the inside of the IC. You still need to be certain that there is a fairly large resistance to limit the current. I have done it with as low as 1K ohms but it is better if it is higher.

I can say I did test the inputs with high levels. It was in the lab and I wanted to get a compressor curve or THD verses level or something like that. As I was setting it up I pulled up the test file and did not notice right away that the level sweep was going to start at like +27dBu. Needless to say, after only 30 or 40 seconds of this the part died. So I can say I did test this and you can blow up the part with too much level. It is one of those Duh? moments we all have done when working on projects.

I hope this helps.

Dave T