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  • Case ID: 323922
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LDO and DCDC pinout configuration

Dhruvit

Hello,

I want to ask about the nRF52840. In normal mode, it operates in LDO mode, but we can configure it to DCDC mode for more power-efficient operation.

I've read the datasheet up to page 65, but I'm still unclear on how the LDO output is used. I believe it uses the VDD pin as its output, since there's no separate LDO pin.

Now, I'm referencing a project where the nRF52840 is powered by a battery through a PMIC (Power Management Integrated Circuit) that outputs 2.5V. However, the project uses a different configuration (referring to the SB1/SB2 jumpers).

(Here 3v3 node i am getting 2.5v, and SB1 - SB7 jumper is normally shorted where as VIN pin have 5v USB power. )

Based on this, I assume that if they wanted to use the LDO, they would just short SB2 and unshort SB1 to get the 2.5V output on the VDD pin. Is that correct? 

Thanks & Regards 

  • 0

    Hi Dhruvit,

    The LDO, as you already know, does no have a "dedicated" output. The device either operates in LDO or DCDC. 

    Yes, to make it in LDO, you need to short the SB2 and open the SB1. 

    The DCCH to VDD connection is not really necessary, but it's fine to leave it there as long as you have DCDC disabled in the registers. 

    Do keep in mind that in LDO mode, it's okay to leave the external components for DCDC there, but in DCDC mode, if there are no external components mounted, then this can damage the device.

    Regards,

    Priyanka

  • 0 in reply to Priyanka

    Hi Priyanka,

    Thank you very much for the clarification! That makes perfect sense now.

    I appreciate you confirming that shorting SB2 and opening SB1 configures the LDO mode. It's also helpful to know the DCCH to VDD connection isn't necessary but can be left for LDO operation.

    I'll be sure to keep in mind the potential damage from missing external components in DCDC mode.

    As I'm still studying the datasheet, I might have further questions in the future. Would it be alright to keep this thread open, or should I create a new one?

    Thanks again for your assistance!

  • +1 in reply to Dhruvit

    Hi Dhruvit,

    Yes, for queries related to something in this ticket, you can continue with more queries here itself, and for something that's different, feel free to create a new ticket.

    We are happy to assist Slight smile

    -Priyanka

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