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nRF52840 High Voltage Mode Configuration with SWD

rikhard

Dear nRF,

My questions are related to high voltage mode of nRF52840 and SWD. My target is to design as high performance solution as possible and current consumption will not be an issue.

I have been following Reference Circuit #2 (QIAA), found from this link.

Input voltage is 5V1 for the nRF, supplied from switching regulator and equipped with decent amount of ferrites and bypass caps.

I appreciate if you can answer to the following questions:

  • Will I need to configure the firmware of nRF to enable internal LDOs or is the powering selection automatic?
  • How do I choose correct voltage settings provided that the nRF52840 ICs are shipped empty ones, with no FW inside? Is there any documentation about this?
  • Which are the benefits to use low voltage mode or high voltage mode? In HV mode, buck regulators are not needed and I assume there will not be problems with spurious (interferers) ?
  • SWD with high voltage mode, should I connect the VDD_nRF from external nRF52840-dk to the my custom board net VDD_nRF at pin W1 via pin header in order to maintain correct voltage level for SWD operations? I assume my 5V1 power supply should be disconnected when doing this operation.

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    Hello,

    Will I need to configure the firmware of nRF to enable internal LDOs or is the powering selection automatic?

    By default the LDO regulators are enabled, and you do not need to configure it. But you should make sure that the DC/DC regulator is not enabled in firmware, seeing as enabling this without the external LC filter will render the chip unusable until the external LC components are added.

     

    How do I choose correct voltage settings provided that the nRF52840 ICs are shipped empty ones, with no FW inside? Is there any documentation about this?

    Are you referring to the configuring whether normal or high voltage mode is used or how to select the output voltage of the REG0 regulator stage?

    The voltage mode is automatically detected based on where the supply voltage is connected, if it is connected to both VDDH and VDD the system enters normal voltage mode, if only VDDH is connected the system enters high voltage mode. More information on the voltage regulators can be found here: https://infocenter.nordicsemi.com/topic/ps_nrf52840/power.html?cp=4_0_0_4_2

    The output of the REG0 regulator stage is configured in the UICR, https://infocenter.nordicsemi.com/topic/ps_nrf52840/uicr.html?cp=4_0_0_3_4_0_7#register.REGOUT0

     

    Which are the benefits to use low voltage mode or high voltage mode? In HV mode, buck regulators are not needed and I assume there will not be problems with spurious (interferers) ?

    There is no difference in performance between normal(low) and high voltage mode other than the current consumption.

     

    SWD with high voltage mode, should I connect the VDD_nRF from external nRF52840-dk to the my custom board net VDD_nRF at pin W1 via pin header in order to maintain correct voltage level for SWD operations? I assume my 5V1 power supply should be disconnected when doing this operation.

    High voltage mode can be used with SWD, but then the programmer must not supply voltage to the board. This means that when using the nRF52840DK as a programmer the solder bridge SB47 must not be shorted. VDD_nRF of the custom board must then be connected to the VTref pin of the 10-pin debug connector.

     

    Best regards,

    Bendik Heiskel

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