How to use P21 external supply in nRF52833 DK

[Ziyao Zhou]

Hi,

I am using nRF52833 DK and power it using P21 External supply. I connected P21 with the power profiler 2 and give 1.8V.  It works for serveral days, however, today I notice when I give 1.8V the program will not run. If I change to around 2.2V, it start running.

I have three questions:

1. What happen to the DK, before it can work under 1.8V, now it cannot.

2. When I am measure the current through P21, with all default setting(VDD power source, vEXT-nRF off, default), am I measuring the total current consume by the nrf52833 and interface MCU?

3.Can P21 use together with Lipo battery, if I connect a battery here, is there any battery management circuit after P21.

I have found some schemetic but I have no clue about what is happening in this DK. Thank you so much for your time!

[Simonr]

Hi

From the nRF52833 DK 

"To avoid voltage differences on the DK, the external supply is also connected to the input of the voltage follower when the VEXT->nRF switch (SW10) is in the ON position. The voltage follower circuit requires 5 V supplied to the DK. The voltage follower can be disconnected from the External supply by cutting SB58. To prevent leakage due to voltage differences, the DK should be set in the nRF only mode."

So if you're measuring current while powering the board from P21 with SW10 set, the PPK2 should not be used as a Sourcemeter, but rather an Amperemeter since it already has an external supply in this mode. I think you're seeing a lot of leakage having multiple power sources here.

Best regards,

Simon

[Ziyao Zhou]

Hi

Thank you for your reply! Does that mean I cannot use PPK to be the external supply in P21, I just want to use it as a stable voltage source.

By the way, what is the voltage follower? Does that mean the P21 must have a voltage higher than 5V?

[Simonr]

Hi

As explained, the P21 supply must be supplied with between 2.5 and 5.5V. The voltage follower circuit is there to make sure there aren't any mismatches betweent he external supply and the USB supply. Yes, the PPK2 can be used as a supply on P21, but this isn't its intention. If so, the DK should also be set in the nRF Only mode to prevent leakage currents due to voltage differences on the board (this is SW6 on the DK).

Best regards,

Simon