mfrc522 hardware design

[effitahar]

Hello, i designed a basic RFID reader based on MFRC522 reference design and antenna matching calculation.

when trying to test the board I can see there is communication with the reader, but no tag identification, I suspect something in my hardware design is wrong, can you please advise?

[Tomas_Parizek]

Hello effitahar, 

I would fully recommend checking your antenna parameters and matching them with the VNA. For this NFC Controller, the target impedance is around 40 Ohms.

Regarding the  Crx, Cvmid, R21 and R22. For now, I would keep them default.

BR

Tomas 

[effitahar]

Thanks! I would do it,

Regarding the default value, I haven't found formal reference for it

[Tomas_Parizek]

Hello effitahar,

Ok, great!

Also, consider that the mfrc522 is quite an old product and it i not recommended for new designs. I would recommend considering CLRC663 where we can offer better support.

BR
Tomas

[effitahar]

I understand, unfortunately the software was already developed based on development board, for the next design we will use updated hardware.
But really strange that the datasheet can't give any information regarding 2 important component...
Thank you for your help

[Tomas_Parizek]

Hello effitahar, 

What about the impedance tuning? Did you do a measurement with a Vector Network Analyzer? Please check this app. note -> https://www.nxp.com/docs/en/application-note/AN12810.pdf

BR

Tomas 

[effitahar]

Another thing, I can't find in the datasheet the target impedance for mfrc522

[effitahar]

Thanks, I haven't done it yet, for my understanding it's fine tuning and the reader should work in non optimized way, even before. 

All of my calculations based on the pcb antenna dimensions and properties (when I designed antennas for passive tags it worked properly)

Could you please look at Crx, Cvmid, R21 and R22 values and connection?

Those components are copied from reference I found and I really not sure regarding it.

All the other components I calculated using the nxp online and excel tool.