Switching circuit between battery (VDD) and USB power (VDDH)

[hillstub]

Dear all,

I'm designing a circuit that should allow powering the nRF52840 board with either an USB power supply (USB2) or a (non-rechargeable) CR2032 battery (B1). According to the reference schematics, in the former situation only VDDH need to be connected, while in the latter, VDD and VDDH need to be connected. To limit voltage drop, I'm thinking of implementing P MOSFETs (Q2, Q3):

Would this work or are there other/better solutions? 

Thanks a lot in advance!

[JONATHAN LL]

Hi,


We do have a solution that uses USB and coin cell battery's as power source, the nrf52840 DK. Maybe you can have a look at how it is done there, here is a link to the HW. 


When you say USB power supply is that a battery also? If this is not battery then using any regulator that goes from 5V to 1.7-3.3V will do the job and you cans tick to normal voltage mode instead of having to switch between High and normal voltage mode.  

Regards,
Jonathan

[Serafino Convertini]

Hi, I'm trying to reach the same goal. I would power a nRF52840 on my custom board both eith a cell battery (specificaly CR2032) and the VBUS provided by the USB connection.
I was thinking using two schottky diode in the way showed in the attached image with using the internal DCDC of the nRF52840 as in the development board.

I didn't realize yet the board, so I cannot say you if this solution will work, but It seemes that you solution is better.

JONATHAN LL in the proposed configuration that coud be downloaded in the page you link, I cannot find a solution for this issue. Am I wrong in something?

Thank you in advance

[JONATHAN LL]

Hi Serafino Convertini , 


Can you create a new ticket referencing this one, and we can follow up with specific details there if needed. 


You can have a look at the circuits for the  development kits and you will see there is a section there for switching what voltage is the source for the nRF. 

Here is a link to the section: https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/vdd_power_sources.html?cp=5_0_4_7_2_1 

Regards,
Jonathan