Wireless charging circuit

[Dajgoro Labinac]

Hi

What would be the best way to interface a wireless charging circuit with a nRF52 device? I've found a IC from Texas instruments that does the job, but is it safe to have the charging receiving coil around the NFC antenna of the nRF52? Would the induced currents from the wireless charger cause issues to the nRF52? Also, if not, is there a way to use the same antenna for charging with the dedicated charging chip and have it still function as the nRF52 NFC antenna so a single antenna coil can be used instead of two separate ones. Antennas have to be packed together due to device size.

[Hung Bui]

You may need to consider the frequency of the wireless charging, which technology it uses inductive or resonant. There could be interference between the NFC antenna and the wireless charging antenna. We would suggest to avoid placing them close to each other. And definitely you can't combine the 2 antenna together , at least on our chip.

[Dajgoro Labinac]

Ok, so its two separate antennas, my only worry is if there is a scenario in which the induced currents damage the nRF52 NFC front end. Or could I maybe mediate the problem by adding protection diodes to the NFC antenna coil?

[Hung Bui]

I actually don't know much about NFC, but I would assume then you will have trouble receiving NFC signal.

[Quark]

Hi Dojgoro, I hope this find you well. I am currently doing a similar product development with NFC + Qi. I was wondering how you product is now. Did you find a solution and solve the problem. If possible, would you share your experience? My design is that NFC and Qi will not both work at the same time. Whenever wireless charging is detected, nrf52 must be deactivate and NFC only works when not charging. Thanks in advance.

[Dajgoro Labinac]

Hi.
Actually yes, I found a solution that works, and its rather straightforward.
All you need to do is add a 1nF capacitor in series with the NFC antenna (after the 300pF caps) and that will prevent low frequency qi currents from overloading the IC, while the NFC will remain unaffected.