nRF52 NFC and wireless charging

[Colm]

Hi,

I have been developing with nRF51 for some time and already implemented a nice 13.56MHz wireless charging circuit. Now that I'm moving to nRF52 I would like to keep my wireless charging coil / circuit as is, but also be able to use nRF NFC functions.

So, is it possible to use the same coil for WPT and NFC? I've been considering changing the WPT frequency, but do I really need to? If anyone has experience of this challenge, or some tips the would be most appreciated

Thanks

[ovrebekk]

Hi

The NFCT peripheral on the nRF52 series is not designed for a scenario where the antenna is used for WPT at the same time as connected to the NFC1 and NFC2 pins on the device. We are not aware of customers that have used the same antenna for WPT and NFC communication on the nRF52 series.

nRF52 have protection circuitry on the NFC pins to prevent the device being damaged in the presence of a excessive voltage. The protection circuitry may limit the power transfer capability for your charger circuitry. Maximum allowable current flowing into NFC1 / NFC2 is 80 mA peak and clamping voltage is in the range 2.2 while NFC is inactive. If you are planning to switch the antenna between the charger circuit and nRF52, the series switches needed will introduce resistance and will limit the load modulation performance of the system and therefore limit the read distance

That said, we have not tried to combine the coil for WPT and NFC communication on nRF52, so solutions may exist.

Best regards
Torbjørn