A week ago, I asked about this warning in the product specification:
"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."
After some additional reading, I also see this:
"When configured as NFC antenna pins, the GPIOs on those pins will automatically be set to DISABLE state and a protection circuit will be enabled preventing the chip from being damaged in the presence of a strong NFC field. The protection circuit will short the two pins together if voltage difference exceeds approximately 2V."
So, in the presence of a strong NFC field, with the NFC protection circuit active, does one still risk driving reverse current flowing out of the VDD pins and back into the battery? To me, it seems that the 2V differential voltage limit on the NFC pins should ensure that the ESD and parasitic body diodes remain off, even if VDD = 1.8V.
Can you share a more detailed schematic of the internal circuitry connected to the NFC pins? It would be helpful to be able to see for myself the internal circuitry connected to the NFC pins.
Thank you, Kyle
