This is in reference to the note in the manual that says:
6.14.11 Battery protection
If the antenna is exposed to a strong NFC field, current may flow in the opposite direction on the supply
due to parasitic diodes and ESD structures.
If the battery used does not tolerate return current, a series diode must be placed between the battery
and the device in order to protect the battery.
We are considering adding an NFC antenna to our product. We will be using a lithium coin cell for power.
I want to determine if adding the series diode is really necessary for us I'd like to avoid the voltage drop if it not necessary.
Did Nordic really find some issues with using a primary cell with a NFC antenna during their testing. If so how did you generate a strong enough NFC field? Were you using a reader or was it more of a test lab scenario with a transmitter coil driving a high field into the receiver coil? Were you testing a realistic use scenario? Did you just see current flow out to the external supply or battery or did you have something bad happen to a battery?
The nRF52840 DK lets you use a coin cell and and an NFC antenna. Is that a scenario that would require the series diode for a real world application? Could test this with a real world NFC reader and possibly see if the problem would realistically surface?
We might only use the NFC for device provisioning at the factory so we would have control of the reader used and the placement of it relative to the receiver antenna. Given this use case I feel like our risk of any adverse event is really low. What do you think?
