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andrew55529
Visitor II
September 7, 2025
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ST25R3911 – Possibility to disable VDD_IO in Wake-Up mode

  • September 7, 2025
  • 1 reply
  • 321 views

Hello,

I’m working with the ST25R3911 NFC reader IC in a battery-powered application where ultra-low power consumption is critical.

  1. Is it allowed to completely switch off VDD_IO while VDD is still supplied (e.g., when the device is in Wake-Up mode)?

  2. Will the interrupt pin still work in Wake-Up mode if VDD is present but VDD_IO is off?

  3. I noticed that even when VDD is off, if VDD_IO is connected, there seems to be additional leakage current. Could you clarify the expected current paths in such cases?

  4. Is there any recommended sequence for powering up/down VDD and VDD_IO to avoid unwanted currents or undefined states?

  5. Can VDD_IO be powered directly from a microcontroller GPIO pin (to save power by enabling it only when needed)? What is the typical consumption of VDD_IO in idle conditions?

    This topic has been closed for replies.
    Best answer by Ulysses HERNIOSUS

    Hi,

    ad 1) Should be possible. But as detailed in 2) you want to get informed, right?

    ad 2) VDD_IO is needed to drive digital outputs of the chip including IRQ line. So if you want to be notified wake-up mode about changes in the antenna tank you need to supply this pin.

    ad 3) Did you check bits lf_clk_off and out_cl, to assure not driving MCU_CLK?

    ad 4) no special recommendation, I am not aware of any problematic sequences.

    ad 5) Maybe yes - depending on drive strength of MCU and sinking of inputs of MCU.

    How much of unwanted current do you see? I would first thoroughly check point 3) and all possible output pins of the chip to minimize its current before going into switching on/off the VDD_IO.

    BR, Ulysses

    1 reply

    U
    Ulysses HERNIOSUSAnswer
    Technical Moderator
    September 8, 2025

    Hi,

    ad 1) Should be possible. But as detailed in 2) you want to get informed, right?

    ad 2) VDD_IO is needed to drive digital outputs of the chip including IRQ line. So if you want to be notified wake-up mode about changes in the antenna tank you need to supply this pin.

    ad 3) Did you check bits lf_clk_off and out_cl, to assure not driving MCU_CLK?

    ad 4) no special recommendation, I am not aware of any problematic sequences.

    ad 5) Maybe yes - depending on drive strength of MCU and sinking of inputs of MCU.

    How much of unwanted current do you see? I would first thoroughly check point 3) and all possible output pins of the chip to minimize its current before going into switching on/off the VDD_IO.

    BR, Ulysses

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