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VBUS supply before system ON on normal voltage mode nRF52833

deep_dive

1. Our system is configured with circuit config3 of the nRF52833 WLCSP, where an external power supply of 1.8V is applied to VDD.

Power sequence : USB connection -> VBUS supply -> external LDO 1.8V output -> nRF52833 VDD supply 

Due to the turn-on time delay of the external LDO, the V_USB pin (for VBUS & USB Type-C detection) is supplied before the VDD 1.8V of the nRF52833.

Is it OKAY?

In other words, is it okay for V_USB at 5V to be supplied before VDD at 1.8V in a system configured for normal voltage at 1.8V?

2. According to the datasheet section 5.3.2,when the system is OFF and VUSB is applied, the system turns ON.

Does this mean that the system will turn ON regardless of whether the system circuit configuration is in high voltage mode or normal voltage mode?

3. If the system turns ON when VBUS is connected while in normal voltage mode and the system is off, I thought this is because the VUSB LDO is working.

Are the VUSB internal LDO and the VDD internal LDO different from each other?

  • 0

    Hello,

    I have checked the documentation and couldn't find anything specific about the proper sequence.

    I will check internally and get back to you when I'll have more information.

    Are the VUSB internal LDO and the VDD internal LDO different from each other?

    From the documentation it looks like they are separate. VUSB internal LDO is used for the data pins.

    Best regards,

    Michal

  • 0 in reply to Michal
    deep_dive said:

    1. Our system is configured with circuit config3 of the nRF52833 WLCSP, where an external power supply of 1.8V is applied to VDD.

    Power sequence : USB connection -> VBUS supply -> external LDO 1.8V output -> nRF52833 VDD supply 

    Due to the turn-on time delay of the external LDO, the V_USB pin (for VBUS & USB Type-C detection) is supplied before the VDD 1.8V of the nRF52833.

    Is it OKAY?

    In other words, is it okay for V_USB at 5V to be supplied before VDD at 1.8V in a system configured for normal voltage at 1.8V?

    2. According to the datasheet section 5.3.2,when the system is OFF and VUSB is applied, the system turns ON.

    Does this mean that the system will turn ON regardless of whether the system circuit configuration is in high voltage mode or normal voltage mode?

    Thank you Michal

    Could you check my previous other questions? 

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