topic Re: PN7462 RF power consumption in NFC

PN7462 RF power consumption

tommyb90 — Mon, 13 Feb 2023 17:03:22 GMT

Hi to all,
I'm working on an authentication project that involves the PN7462 and I have a problem while using the chip RF interface.
I have a PNEV7462C board where I made the necessary modifications in order to run at 3.3V.
I therefore don't have access to the TVDD generation.

The board also acts as a SPI slave to another microcontroller that manages its functionalities.
The board can receive different commands such as operations on the GPIO pins or enabling/disabling the CLIF interface.

What I found out is that when I ask for detection on the CLIF interface without finding any card near it the current consumption rises and I the phhalHw_PN7462AU_FieldOff function does not really disable the external field.
Is there a command to avoid this behavior?

I tried implementing a STAND-BY mode, but waking up from SPI does lead to issues while transmitting.

Thank you in advance.

Re: PN7462 RF power consumption

Fabian_R — Tue, 14 Feb 2023 17:58:45 GMT

Hello sir,
Thank you for submitting your case to our community, we really appreciate it!
Since we don't have knowledge that the FieldOff function could not be disabling the field.
Could you please share with us the debug messages when this issue is occurring? This malfunction could be due to an issue with the function parameters.
Also, if you could share with us the code section when this procedure is called would be very helpful.

Re: PN7462 RF power consumption

tommyb90 — Wed, 15 Feb 2023 09:51:41 GMT

Hi Fabian_R,
thank you for the quick response.

I used as a starting point the phExMain_mcux example with RTOS and modified it to allow communication on HIF configured as SPI slave.
Inside phExMain_ClifTask, as first operation of the infinite loop I tried executing different codes to solve the following issue.
Maybe I didn't explain the problem correctly. I leave attached a sample of the current consumption of the chip.
The highest peaks are the TAG readings; once the reading is finished, depending on the TAG presence, there is a constant current consumption that persists even if no reading is requested. If no TAG is detected the level is higher.
I disabled LPCD through EEPROM, but I didn't notice any changes. I suppose it is the AGC function keeping the current high in order to detect another presence.
Is there a way to avoid this behavior?
Thank you in advance.

Re: PN7462 RF power consumption

tommyb90 — Wed, 15 Feb 2023 09:53:05 GMT

Sorry I think there was an error while loading the attachment