I want to implement a NFC antenna for the M24SR64-Y on a 10 layer PCB. Have somebody any idea how to do this? Space area is around 2x2cm Thanks

[Henry Crane]

Hello,

our NFC antenna module in eDesignSuite (https://www.st.com/content/st_com/en/support/resources/edesign.html, START DESIGN->RF Design-> NFC antenna design) allows to calculate 1 layer square antennas. It is limited to 15 turns but is a useful tool.

M24SR64 requires a 4.7µH inductance antenna coil for a tuning frequency between 14 and 14.4MHz. 15 tuns with 0.2mm for track width and spacing leads to 4.46 µH. Adding a small parallel tuning cap footprint between M24SR64 and antenna allows to adjust the tuning frequency on board.

please read Application Note AN2972 "How to design an antenna for dynamic NFC tags" for more details on antenna design and validation for our NFC dynamic tag IC families.

best regards,

Henry Crane NFC/RFID support team

[DSomm]

Hi Henry,

15 turns with 20mm length leads to around 4.46uH.

I have a 10layer board. What do you think, would it be better to use one coil on one layer like simulated in edesign or to use two coils on layer1 and 10 with dimensions like on the eval board "ANT7-T-M24SR64" ?

One coil with dimensions on the aval board leads to around 1.32uH. Is the coupling factor so big, that two antennas (top/bottom) will lead to 4.7uH ?

Regards

Daniel