ST25R95 maximum voltage of VRX1/2?

[tyassin]

Hello,

Just a clarification question. When going through the application note (AN5248) for ST25R95. It mentiosn at one point there is a maximum allowed voltage on RX1 and RX2 which should be below 7V.

Where in the datasheet is this specified? 

Thank you.

[Brian TIDAL]

Hi,

as far as I know, table 52 of the ST25R95 datasheet defines the maximum value for VRx1-Rx2 (Differential input voltage between pins RX1 and RX2). 

In AN5248, the measurement in §5.1 step 3.d is ST_R0 (see "adjust the ZRX component value to limit the voltage measured on ST_R0 below 7 V.") whereas §3 refers to VRX1-RX2 which is a differential value. @Henry Crane, can you help to clarify this?

Rgds

BT

[tyassin]

Hi,

Yes table 52 is also the only place where I found any voltage level specified for the receiver.

The 7V mentioned in the app note, I don´t see why or where they come from.

Thank you.

[tyassin]

Hi,

Was there anybody who knew where these 7V originated from?

[Henry Crane · Accepted solution]

Hello All,

foot note 3 in table 47 of ST25R95 datasheet states that the maximum peak-to-peak voltage for (Vrx1-Vrx2) differential voltage is 18V, that is 9V peak. All signal exceeding 9V may be clamped by RX1 and RX2 input circuit protection.

The 7V recommendation in app note relates to this 9V peak level, considering that CW + backscattering level shall not exceed 9V (all calculations documented in app note do not consider tag backscattering but carrier wave signal only).

hope it helped,

best regards,

Henry Crane, NFC/RFID Application engineer.

[tyassin]

Hello Henry,

Thank you for the explanation. That helped.

Br.