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USB supply without VDD supply in nRF52840

what happens when USB supply is powered but VDD isn't powered? The internal USB LDO is working ? DECUSB go to high or not ? Is there a leakage current from usb to nRF?

Thanks,

  • Hi,

    Please see the nRF52840 POWER section at infocenter.

    High voltage mode is entered when the supply voltage is only connected to the VDDH pin and the VDD pin is not connected to any voltage supply. (USB (VDDH = VBUS), VBUS must be connected to VDDH if USB is to be used)

    The voltage regulators can be configured in several ways, depending on the selected supply voltage mode (normal/high) and the regulator type option (LDO or DC/DC).

    By default, the LDO regulators are enabled and the DC/DC regulators are disabled. Registers DCDCEN0 and DCDCEN are used to independently enable the DC/DC regulators for the two stages (REG0 and REG1 respectively). DECUSB is Decoupling for USB regulator output 3.3 V

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