PN7462 NFC chip does not come back to sleep current(18uA) after first NFC card detection.

[mravi]

Hi,

I am using PN7462AU NFC chip in LPCD mode. The chip is powered with 3.3V supply. The chip takes only 18uA sleep current when powering the chip. It will stay like this till the first card detection. But after first card detection the current goes upto 25 or 35uA and it will not come back to 18uA. The chip comes back to sleep state, but current is high. But if the chip is working with a 3V supply then the chip will come back to its sleep current(18uA) after card detection.  What may be reason? Is it related to the PMU register configuration? Please help me

Regards

Midhun V R

[Kan_Li]

Hi Midhun V R,

Did you test it based on OM27462? Please kindly clarify. I will try to reproduce your issue here.

Have a great day,
Kan

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[mravi]

Hi Kan Li,

We have tested the program with OM27462CDK development kit. But we designed a pcb with the PN7462 for out project, and measured the sleep current on this board not in development board. I observed one thing, when just powering the board the voltage on the pin ATX_B is zero but after first card detection the voltage become 3.3V. It will stay like this. I just pulled down the pin ATX_A with a 1Mega ohm resistor .Then the board is coming back to its sleep current (18uA) after card detection. In our project ATX_A and ATX_B are used for UART communication with a BLE module. When I measure the sleep current BLE is not placed, so ATX_A and ATX_B are open. ATX_A is TX and ATX_B is RX. Why the voltage on the ATX_B becomes high after card detection? Is it something related to UART configuration?

Regards 

Midhun V R 

[Kan_Li · Accepted solution]

Hi Midhun V R,

Thanks for the information! and yes, I think it is due to UART configuration, as ATX_B can act as HSU_TX, and the host interface should not be kept floating according to the data sheet. Please refer to the following for details.

Have a great day,
Kan

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