After checked your schematic and two suggestions for your reference：
1. Vbat is the main power supply of the NFCC, Vdd(PAD) is the power supply for the host interface and GPIOs. Vdd(UP) is the power supply allowing to generate TXLDO. Their typical operating voltages are different. So, Vbat and Vdd(UP) could be connected to 3.3V, and then it would be better to power Vdd(PAD) separately.
2. For the anormal board on your side, it is recommended that you do a comparison test between normal and abnormal to determine whether VDD(TX) pin is within the normal operating voltage range. The voltage level on TX output buffer is coming from VDD(TX) and this pin is powered internally by the PN7160 thanks to the TXLDO block. The output voltage of this TXLDO can be set between 2.7 V to 5.25 V depending on the VDD(UP) voltage.
Hope the above reply can help you!
Thanks for your reply!I have done comparison test between normal boards and abnormal boards,on the normal board VDD(TX) pin is within the normal operaing voltage range,but on the abnormal board VDD(TX) pin is no voltage output.My doubt is that VDD(UP) connected to 3.3V,why do some boards work and some don't work.Then I raised VDD(UP) voltage to 4.0V,the abnormal board works properly.Can you tell me the reason for this problem.
Vdd(PAD) is the power supply for the host interface and GPIOs. I think there may be inconsistencies in the default state of the chip that cause some GPIOs to leak electricity, which leads to some boards abnormal. So, two suggestions for you:
1. Vdd(PAD) Vdd(UP) and Vbat are powered separately, like the following would be better:
2. Initialize all Gpios and the perpherals by software, make sure that the initial state of all boards is consistent.
You can try the above action to see if it works.