That is 1 Ohm between AC0 and AC1 in X-NUCLEO-NFC04A1 ?

[John_zhang]

Antenna is about 5 Ohm and 4.5uH, why is 1Ohm?

[AvaTar]

Probably to disconnect the antenna easily with removing the resistor.

[Denis ROMAN]

​Hello Zhang,

I am really sorry but I don't understand your point.

Denis

[John_zhang]

I hope to design R and L value of the st25dv64 external antenna, not internal PCB antenna by tool. In the AN2972 document, “2.3 Basic equations “ , I don’t know Rs and Cs. So I could not designed antenna of st25dv64. In the other document about M24LR64, Cs is 28.5pF, Rs is 5Ohm. By those parameters, I would calculate R and L of M24LR64 antenna, Ra is 5Ohm , L is 4.5uH. I hope to test real resistor between AC0 and AC1of St25dv64 with the X-NUCLEO-NFC04A1. The test resistor value is1Ohm, not 5Ohm or2.5Ohm. Thanks!

[John_zhang]

Hi,

Thanks for your reply. Which resistor to remove?

Thanks!

BR

zhang

[Denis ROMAN · Accepted solution]

​Hello Zhang,

For ST25DV64k, Cs is also 28.5pF. You thus just need to design/use an antenna which inductance around 4.5uH, there is not need for additional resistor.

Have a nice day

Denis

[John_zhang]

Hello Denis

Thanks.It is important for me.

Have a nice day!

BR,

zhang​