ST25R3911B- DISCO advice

[Csxhades]

Hey,

I want to test an off the shelf Molex NFC antenna 15*15 mm using the ST25R3911B. Is it possible to connect the antenna to the discovery board as I wanna evaluate the antenna whilst connected to the ST25R3911B? If so, how can I test the setup? If not, is there any other way to test other than connecting the antenna to a standalone chip with the matching network and decoupling components?

Thank you.

[Brian TIDAL]

Hi

if I am not wrong the antenna of the ST25R3911B-DISCO can be disabled (just remove the J401, J404 and J405 0 Ohm resistors)  and an external antenna can be connected on J402. See the 

ST25R3911B-DISCO-MB1325 Schematics. The matching network will need to be modified to fit with the external antenna parameters (see AN4974 Application note - Antenna matching for ST25R3911B).

Rgds

BT 

[Travis Palmer]

Hello Csxhades,

every NFC antenna requires its own matching components. The matching network transforms the inductive load of the antenna ( and its antenna specific parameters: L_ant, Cp_ant, Fres,...) to the desired target matching impedance.

There are basically two types of antennas:

1.) Pure NFC antennas which do not contain any matching components (please see AN4974)

2.) 50Ohm NFC Antenna (basically the same as 1.) but with additional matching components to tune the antenna to 50Ohm and adjust its Q-factor (please see AN5592).

AN5592 should also help you determine if your antenna is 1.) or 2.).

br Travis