Hei, We would be using nrf52 chip in a very miniature device that should have both BLE and NFC capability. NFC is needed for just as a tag. Thus, nrf52 is a good option. I have a doubt regarding the NFC impedance interface: According to infocenter.nordicsemi.com/ (Figure 7. NFCT antenna recommendations), two shunt capacitors are required to tune the NFC coil to 13.56 MHz. However, the resistance between the NFC1 and NFC2 varies depending upon the swing voltage and I guess it is in the range of (40 Ohm to 1 kOhm). Usually, for other standard chip (e.g. NXP) this is fixed at 80 Ohm and hence matching network can be designed assuming 80 ohm between NFC1 and NFC2 pin for the NFC antenna so that it resonates at 13.56 MHz. So, my doubt is what would be the value of this resistance between NFC1 and NFC2 for which matching network can be designed? This for sure won't just require two shunt capacitors for tuning to 13.56 MHz but rather some series capacitors as well. Please clarify this doubt. Thank you.
