AD1838A Analog port protection
Do the A/D converter inputs have overvoltage protection above 2.82V p??
Or is it necessary to implement protection zener diodes at these inputs??
hardware
Integrated/Special Purpose A/D Converters
AD1838A
ad1838
Audio CODECs
Hi isbevacqua ,
I noticed that this part is being supported here in this forum (+) Q&A - SigmaDSP Processors & SigmaStudio Dev. Tool - EngineerZone (analog.com). I have moved this thread here so someone from the community can assist you in your questions.
Regards,
JC
Hi JC, Thank you.
When you say "someone from the community" do you refer to an official tech support person from Analog?
Because that's what I'm looking for. Otherwise, I don't know where to ask.
Thank you.
Hello isbevacqua,
The pins will have some ESD protection internally but it is not good to rely on them is the input signal is likely to exceed the max input voltage.
The 2.82V specification you are quoting is for an input voltage that would give you full scale digital input after conversion. This is not the max voltage on the pin. For that I would refer you to the absolute max ratings:
This is 0.3V above the AVDD voltage. It is relative to whatever AVDD happens to be.
So using a Schottky diode to the AVDD would help limit the input voltage. This is good for audio coming out of an OpAmp. However, I would still have some ESD protection right at the input to your circuit and have it dissipate to chassis ground and not signal ground or power. I think it is an error to connect ESD protection to a power rail because it will cause the voltage spike to be felt by everything in the circuit and can blow up the entire circuit. Dissipating it to chassis ground and having a dedicated chassis ground trace will help keep it away from your circuit. But, I have strayed slightly off topic.
Dave T
Hi Dave, thank you for your answer, we are using ESD protection in our system, but my question was more related to audio signals coming out of OpAmps. In certain gain configurations the AD1838 audio input could overpass the limits and we wanted to know if the device has internal protection for that situation, otherwise we are going to implement it externally like you see in this picture.
Is that ok?
Hello isbevacqua,
Yes, this should be good. It will limit the voltage on the pin to around the 0.3V+AVDD limit.
I am expecting there is a series resistor on the output of the opamp? I would not think it is good to directly drive it with a low impedance.
Dave T
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