nRF52832 NFC - ESD protection

[Gal Davidi]

Hi,

I have read this ticket which discusses Qi protection to the NFC  NFC pins broken because of Qi charger? How to do Qi + NFC? 

I also wanted to better understand if i can protect the circuit with ESD/TVS diode.

It is more "protection from wireless charging" to meet regulation testing, rather than ESD. but ESD/TVS can help meet the test requirements

the DS implies there might be ESD diodes integrated in the chip, but i'm not sure.

Thanks.

[Simonr]

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

[Gal Davidi]

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.