NFC Amplitude limited not working? Significant noise on Vdd when Vdd =1.8V (as opposed to 3V)

RE: NFC Amplitude limited not working? Significant noise on Vdd when Vdd =1.8V (as opposed to 3V)

GilesHutchison — Fri, 07 Feb 2020 13:22:15 GMT

Hi Turbo,

Thanks for tyour reply.

The LDO is carefully layed out, and follows the data sheet layout guidelines, and has stitched ground plane on top and bottom layers.

I have a very similar set-up using the EVK running at 3V with 1/10th the amount of noise. I will see if I can configure the EVK to run from 1.8V Vdd / Vdd_IO and provide more feedback.

Regards

Giles

RE: NFC Amplitude limited not working? Significant noise on Vdd when Vdd =1.8V (as opposed to 3V)

Turbo J — Fri, 07 Feb 2020 12:53:51 GMT

I don't thinks its just the pins - it is probably the "high power" NFC field coupled directly.

Check the LDO feedback path in the PCB layout - it must be properly shielded from the 13.56 MHz. Otherwise the LDO might do stupid things.

The NFC high frequency could also affect the oscilloscope probe (or the GND return path), so I don't really trust any measurement here.