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Switch to power off nrf52840

Pedro J

Hi!

I'm designing a wireless PC peripheral with NRF52840. VDDH is connected to +3V3 from BMS, and VBUS is connected to USB voltage.

Is it necessary to connect VBUS to USB+5V to detect USB?

When I have the device connected to USB and I want to power off the device, do I need to disconnect VDDH only or VBUS too?

Can I put a switch directly or this is dangerous due to the transients and I have to use mosfets?

Thanks regard.

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  • +1

    Hi Pedro,

    Is it necessary to connect VBUS to USB+5V to detect USB?

    Yes, the VBUS is required for the USB peripheral to function properly. It helps to detect whenever the device is connected to host device. Theoretically it should be fine to connect VBUS to any 5V source, but then you might get problems when using USB, i.e. for USB detection, etc.

    When I have the device connected to USB and I want to power off the device, do I need to disconnect VDDH only or VBUS too?

    Well, as mentioned earlier, the VBUS is not used for "powering" the device. So if you power the device using USB, then you will have to disconnect the USB in order to power off the device. And if you are not using USB to power the device, then you might be using VDD or VDDH. So then this needs to be disconnected.

    Can I put a switch directly or this is dangerous due to the transients and I have to use mosfets?

    Where exactly are you planning on using a switch?

    Best Regards,

    Priyanka

Reply
  • +1

    Hi Pedro,

    Is it necessary to connect VBUS to USB+5V to detect USB?

    Yes, the VBUS is required for the USB peripheral to function properly. It helps to detect whenever the device is connected to host device. Theoretically it should be fine to connect VBUS to any 5V source, but then you might get problems when using USB, i.e. for USB detection, etc.

    When I have the device connected to USB and I want to power off the device, do I need to disconnect VDDH only or VBUS too?

    Well, as mentioned earlier, the VBUS is not used for "powering" the device. So if you power the device using USB, then you will have to disconnect the USB in order to power off the device. And if you are not using USB to power the device, then you might be using VDD or VDDH. So then this needs to be disconnected.

    Can I put a switch directly or this is dangerous due to the transients and I have to use mosfets?

    Where exactly are you planning on using a switch?

    Best Regards,

    Priyanka

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