ST25RU3993-HPEV - Use of power detector component MAX4003EUA+T (U3)

[TNgo.1]

Dear ST engineers,

To my understanding, the use of the power detector component is to help the MCU determine the actual power output from the reader (before entering the antenna).

May I kindly check with you the reason behind the selection of the model MAX4003EUA+T ?

• Based on its datasheet (https://datasheets.maximintegrated.com/en/ds/MAX4003.pdf), under the Absolute Maximum Ratings session, the max RF input power to the chip is 6 dBm.
• The RFID reader, when using the external amplifier, is capable of reaching 30 dBm of RF power. In this case, after using the 20-dB coupler, the input power into the detector chip will still be around 10 dBm. Taking into account loss, the power might be around 7-8 dBm, which is still higher than the 6 dBm maximum rating.

It would be great if you can help to share with me your testing experiences with this module, if there is any issue, as I am currently in the process of designing my own RFID reader based on ST eval board.

Thank you very much for your kind support.

Best regards,

Ngo Tung

[Bart Herse · Accepted solution]

Hello TNgo.1,

note that the input of the power detector is protected by a Pi pad attenuator (R24, R25, R45) with 20 dB of attenuation.

For the HPEV board the detector voltage stays below 1.3 V for max RF power output.

Cheers,

B

[TNgo.1]

Dear Bart Herse,

Thank you very much for your kind input.

Regards,

Tung