I have a custom board with the PN5180 and I'm using it to emulate an NFC tag. I am able to read the tag with a phone at a distance of about 2.5cm, but after doing this once or twice, the antenna sensitivity seems to drop really low and I have to move the phone really close to the antenna (about 1mm distance between antenna and phone).
I noticed that I can reset the PN5180 and this will bring the range back up to 2.5cm, but again, it will fall to 1mm after scanning the tag once.
I have done the same test on the PN5180 development board (PNEV5180B) and I am consistently able to read the tag from a distance of about 3cm (no sensitivity issues).
Is the PN5180 automatically adjusting sensitivity? Do I need to change the value of NFCLD_SENSITIVITY_VAL in the PN5180 EEPROM??