Hi,
I'm working on a industrial input/output combination which needs to be certified for SIL level 2. For this I want to be able to test if my input is still working correctly. To do so I have the following circuit;
Now I have 2 questions regarding this:
- I want to verify the correct working of my input (for diagnostics), therefor I am switching the FGnd with a MOSFET to logic GND, should there be any decoupling between these?
- For my input protection I'm using a Pi filter, a freewheel and TVS diode, however I'm not sure if the chosen TVS diode is the needed size (possibly too big), any hints on how I can calculate the correct specs for this, as in the ISO1211 datasheet much smaller TVS diodes are recommended.