Impedance matching circuitry on X-NUCLEO-NFC03A1

[lcopparoni]

Hi everyone,

I'm facing some issues while trying to understand if (and eventually how) it's possible to use a different antenna using an X-NUCLEO-NFC03A1 evaluation board.

I know I may just use the bare ST25R95 chip and then realize an impedance matching circuitry to it, but for timing reasons I'm trying to understand if it would be possible to do that with all that's offered with the NFC03A1 evaluation board.

Still, I have some questions and doubts:

1) Is it possible?

2a) if possible, how can I do that? In the ST25R95 datasheet is only reported the differential output impedance, but in the X-NUCLEO-NFC03A1 there is only a schematic with the whole matching circuitry after ST25R95 TX1 and TX2 pins, so it's not clear how to do that.

In fact I have a custom antenna which is a MUST to be used for my application, and I need to use it instead of the one integrated in the NFC03A1.

2b) If not possible, I found the X-NUCLEO-NFC06A1 which uses the ST25R3916 reader, which has an AAT possibility controlled by firmware and also a tool from ST which lets you calculate the matching circuitry after inserting custom antenna parameters into it. This would be easier maybe?

Can someone please help me?

Thank you in advance!

[Travis Palmer · Accepted solution]

Hello lcopparoni,

we have dedicated application notes for each product, which describes how to do the antenna matching.

For example the antenna matching for the ST25R95 is described in

AN5248 ST25R95 transceiver antenna tuning circuit with EMI filter.

AN4974 Antenna matching for ST25R3911B/ST25R391x devices you can find information about matching the antenna for the ST25R3911B devies and

AN5276 Antenna design for ST25R3916, ST25R3917 and ST25R3920 devices describes the antenna matching for ST25R3916 devices.

Each document (and documents related to other topics) can be found at the documents section of the landing page of device. For example: ST25R3916 - High performance NFC universal device and EMVCo reader - STMicroelectronics

Following this guide, you should be able to remove the antenna of the NFC03A1 and replace/connect your custom antenna. Afterwards you have to measure the antenna and calculate the matching component values using the excel tool available on st.com.

br Travis