Part Number: ISO7760
Dear e2e support,
My customer needs to protect the ISO7760F inputs from high voltages (up to 90V during several seconds), in case of dysfunctions inside his system/application.
So the ISO inputs have been protected by series resistors (30 to 50Kohms).
Under these conditions the diodes at the input stage of our ISO will get a ~3mA current, right?
Do you see any issue with this architecture?
would you recommend other resistor value?
What would be the max current that our diodes could handle under the following conditions ?
- during 5s,
- at 70°C,
- only 2 diodes among the 6 are clamping the current (the others are not active)
Note that after these 5s, the ISO can be out of order or defective. This is not an issue, regarding how it's managed in the final application.
Thanks for sharing the details related to your question.
The internal bypass diode is an ESD diode which is ideally meant to support on HBM ESD pulse and is not meant for continuous operation. Hence, the best way to protect input circuit is to clamp the voltage by using either a TVS diode (for transients) or a Zener (for continuous).
I also see you have mentioned that the internal diode only needs to handle about 3mA current for 5 seconds and it is okay for it get damaged after. If my understanding is correct then this should be okay. I recommend customer to test the devices sufficiently by applying the 90V at the device inputs with the series resistors.I would like say it once again that the internal ESD bypass diode of ISO7760 will not be able to support continuous operation of any current. Thanks.
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