nRF52832 NFC - ESD protection

RE: nRF52832 NFC - ESD protection

Simonr — Wed, 05 Oct 2022 06:54:47 GMT

I discussed this with a colleague, and in our experience this hasn't been an issue in the past, and that the ESD/TVS diodes shouldn't be necessary, but we strongly recommend that you test this, and perhaps make space for it in your prototypes to be able to test with and without diodes like this. If you decide to add diodes as a precaution that should be fine at least.

Best regards,

Simon

RE: nRF52832 NFC - ESD protection

Gal Davidi — Tue, 04 Oct 2022 08:42:04 GMT

Hi Simon,

The idea here is to pass IEC 60601-1-2 (immunity to proximity magnetic fields)

This link explains the test:

https://absolute-emc.com/article/IEC-60601-1-2-ED.4.1-New-requirement-immunity-to-proximity-magnetic-fields

I am not sure how to convert the radiated field in to current at the chip's input, but I would like to protect it as much as possible.

Do you have any other recommendations?

Thanks for your support,

Gal.

RE: nRF52832 NFC - ESD protection

Simonr — Tue, 04 Oct 2022 06:51:12 GMT

First off, the maximum input current on the NFCT pins is 80mA according to the NFCT Electrical specification. There is an NFC protection circuit that can be enabled with the NFCPINS.PROTECT=NFC. Then a protection circuit will be enabled on the dedicated pins, preventing the chip from being damaged, as the NFC pins will be shorted together if the voltage difference exceeds 2V. This is the only protection in the NFC circuit by default. But yes, also adding a capacitor should provide some NFC protection. What QI currents are you expecting to see?

Best regards,

Simon

RE: nRF52832 NFC - ESD protection

Simonr — Mon, 03 Oct 2022 15:49:42 GMT

We are looking into this issue. I will get back to you tomorrow with more information.

Best regards,

Simon