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Rob_Talor
Visitor II
February 3, 2025
Solved

ST25R3916 VDD_RF regulator bypass mode

  • February 3, 2025
  • 1 reply
  • 540 views

Hello!
Is there any additional information about on how to use on ST25R3916 the bypass mode of internal VDD_RF regulator to be able to a transmitter output current higher than 350 mA (up to 500 mA) supplied from an external source.
In ST25R3916 datasheet only gives this information:
"If a transmitter output current higher than 350 mArms is required the VDD_RF regulator cannot be used to supply the transmitter. VDD_RF and VDD_DR have to be externally connected to VDD_TX (connection of VDD_RF to supply voltage higher than VDD_TX is not allowed)."
Also i see in the ST25R3916 Discovery Board (MB1414B) schematic open jumper J206 and unplaced decoupling capacitors C209, C210.
What are my steps to enable VDD_RF regulator bypass mode? Only close jumper J206 and placed capacitors C209, C210? Is there anything also that needs to be done?

Best regards, Rob.

    This topic has been closed for replies.
    Best answer by Travis Palmer

    Hello Rob_Talor,

     

    Bypassing the internal regulator means, connecting the VDD_DR/RF directly to VDD_Tx. 

    On the MB1414-B this can be done by closing J206. 

    AS stated in the Absolute maximum ratings table: "Peak current supplied from an external source, internal
    voltage regulator bypassed". 

    Which means, should measure the temperature of your design and make sure it stays within the specified limit.

    AN5584 (https://www.st.com/resource/en/application_note/an5584-st25r39xx-nfc-reader-thermal-design-stmicroelectronics.pdf) provides further information about measuring the junction temperature.

    Please let us know, if you have further questions.

     

    br Travis

    1 reply

    T
    Travis PalmerAnswer
    ST Employee
    February 17, 2025

    Hello Rob_Talor,

     

    Bypassing the internal regulator means, connecting the VDD_DR/RF directly to VDD_Tx. 

    On the MB1414-B this can be done by closing J206. 

    AS stated in the Absolute maximum ratings table: "Peak current supplied from an external source, internal
    voltage regulator bypassed". 

    Which means, should measure the temperature of your design and make sure it stays within the specified limit.

    AN5584 (https://www.st.com/resource/en/application_note/an5584-st25r39xx-nfc-reader-thermal-design-stmicroelectronics.pdf) provides further information about measuring the junction temperature.

    Please let us know, if you have further questions.

     

    br Travis

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