nRF52840 - Power Sources and switches

[Nikosant03]

Hi everyone,

I am looking the schematic of nRF52840 (PCA10056) and I am a bit confused with the Power Sources (sheet 7 of 7).

There are three load switches that prioritize the power sources. What I understand so far is that when the 5V boost converter is ON then LiPo battery and ext. source are ignored and when ext. source is detected LiPo battery is ignored.

But I cannot understand the schematic. I mean, VSUPPLY line is connected on the input of each load switch.. It shouldn't be connected to the switches' output to get the voltage of the corresponding source (VREG, VBAT, VEXT)?

Also on the schematic, there is the VDD signal. I cannot figure out where is coming from...

1. Where is coming from the VDD signal based on the schematic?

2. VDD value depends on the power source (VDD, VBAT, VEXT)?

Thanks in advance!!

[ketiljo]

You'll find a description of the power supply in the DK's user guide: https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/nrf52840_DK/hw_power_supply.html

[Nikosant03]

Hi, I have already checked the documentation but this actually does not answer my questions... Could you please be more specific?

[ketiljo]

VDD comes connects to VSENSE_SW_OUT via SW8 (power swicth). Then via U17 to VSUPPLY. What supply you have is selected by U13, U14 and U15.

[xiang san]

According schematic diagram，VDD comes connects to VSENSE_SW_OUT via SW8 (power swicth). VSENSE_SW_OUT comes form VSUPPLY via U17,but what is the VSUPPLY come from? 

[ketiljo]

https://infocenter.nordicsemi.com/topic/ug_nrf52840_dk/UG/dk/vdd_power_sources.html