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Best answer by Denis ROMAN

​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

6 replies

AvaTar
AvaTar
Senior III
December 17, 2018

Probably to disconnect the antenna easily with removing the resistor.

John_zhang
John_zhangAuthor
Associate II
December 19, 2018

Hi,

Thanks for your reply. Which resistor to remove?

Thanks!

BR

zhang

Denis ROMAN
Denis ROMAN
Visitor II
December 18, 2018

​Hello Zhang,

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

Denis

John_zhang
John_zhangAuthor
Associate II
December 19, 2018

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!

Denis ROMAN
Denis ROMANBest answer
Visitor II
December 20, 2018

​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
John_zhangAuthor
Associate II
December 20, 2018

Hello Denis

Thanks.It is important for me.

Have a nice day!

BR,

zhang​

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