Measurement issues with PPK 2 on nrf52833 dk

RE: Measurement issues with PPK 2 on nrf52833 dk

Kazi Afroza Sultana — Fri, 05 Jun 2026 13:21:11 GMT

Hello Tobias,

Actually the net is not floating when you have SW8 off and SW9 is et to VDD is the SW6 is on the default position. The net is being back powered through the nRF53833's internal diode. It sits at roughly VDD potential.

The first part of the diagram is U19, an operational amplifier which feeds to base of Q80. Together they are follower who actively forces the rail to the reference voltage. Even we think the buck regulator path is off, but actually not. This loop can hold the node at VDD.

Later you can see two load switches and SB39 solder which gives multiple feed paths. So, even the SW8 switch is off, the rail is being held up by either the opamp follower or VSupply Bypass, that can power the debug MCU and also the led.

You need to set SW6 to the nRF only to disconnect this rail. You can also check SB39 if it is soldered. Then it will couple VSUPPLY to the rail regardless of the position of the switch SW6. So, it needs to be open.

You can try this and measure the current again?

Thanks.

BR
Kazi

RE: Measurement issues with PPK 2 on nrf52833 dk

hifish — Sun, 31 May 2026 21:10:29 GMT

Thank you for the answer

When I tried replicating the measurements I noticed that the usb port (thank you, cheap usb hub)I was using for the devkit was broken / did not deliver 5V.
I do not know how I missed that and I apologize for wasting your time making you search the solution, when the interface USB did not receive power.

My guess is, that using the PPK as a standalone power source is not recommended and will probably result in the irregular / weird behavior I described.
(*Edit It does explain not measuring the led current (2. in the initial post), VDD is most likely sourced by the interface usb)

However I am still curious why this behavior did happen so here is my guess:

Since the nrf52833 does have an internal LDO, VDD_HV and VBUS_nRF do most likely have a connection to VDD_nRF

meaning VDD_HV' / the net colored and
VBUS_nRF' do have a voltage applied to them.

(the Load switch is not bi-directional, the body diode of the p-channel mosfet does not block voltage from Vout spreading to Vin)

The nets to the left of SW9 and VBUS_nRF' are connected to the source of the boost converter

Now depending on how SW9 is positioned either only VBUS_nRF' or both VBUS_nRF and VDD_HV' are connected to the boost source. This would explain the increase in LED brightness, since connecting vbus and vddhv in parallel could supply more current than just vbus

The power switch SW8 does have the option to either connect VBOOST_SRC' to the actual input of the boost converter or enabling a pulldown on the 5V net and cutting power from the converter.
This would match the LED turning off, when SW8 is in "off".

The boost will feed the buck converter for VDD.

BUT this does not answer, why the LED has a supply, when SW8 is on

If SW8 is off and SW9 is (only) on VDD, the LED does also emit light. (VDD_nRF' which is connected to VSRC_NRF which is connected to VDD is most likely powered, but this net should be floating)

And this assumption I made is most likely wrong, since I still do not fully understand the schematic.

Thank you for your time

BR,
Tobias

RE: Measurement issues with PPK 2 on nrf52833 dk

Kazi Afroza Sultana — Fri, 29 May 2026 14:58:09 GMT

Hello,

''Neither the PPK nor the dk were powered for the pictures.
Could you explain further, what you meant with that the enitre board is powered with the PPK?''

The connection I saw from the picture you sent; I observed SW8 is on OFF position. I was assuming that when you measured the power with ppk2, if the connection is like that (SW8 is off, SW6 is on default position and SW9 is set on VDD) then the interface MCU is still connected with the VDD_nRF rail. In such situation, PPK2 is powering both the target nRF52833 chip, all board peripherals (LEDs, pull-ups, sensors) and the interface MCU.

The power for the interface MCU is routed through two load switches. One of the switches is for the VDD supply, and the other switch is for the USB supply. This enables the disconnecting of the interface MCU from the power domain when it is not in use.

These switches are controlled by the presence of a USB connected to the interface MCU USB connector J2 and the state of the nRF ONLY switch SW6. In the picture, these were opposite.

This will increase the current consumption. That's what I meant by saying in my reply.

RE: Measurement issues with PPK 2 on nrf52833 dk

hifish — Thu, 21 May 2026 09:15:58 GMT

Hi,

Neither the PPK nor the dk were powered for the pictures.
Could you explain further, what you meant with that the enitre board is powered with the PPK?

It is self explanatory, that the current for the whole board is measured with the PPK in source mode.
However that was never my question.
(But in meter mode, the current measured was higher than in source mode, when measured in the LED low state.
And the LED current was not measured in meter mode)

RE: Measurement issues with PPK 2 on nrf52833 dk

Kazi Afroza Sultana — Wed, 20 May 2026 12:44:06 GMT

Hello Tobias,

I can see in the picture that your board is not powered by USB. So the entire board is powered by only PPK2. That's why you are observing more current.

RE: Measurement issues with PPK 2 on nrf52833 dk

hifish — Tue, 12 May 2026 15:28:43 GMT

Hello,

I followed the instuctions given on the website https://docs.nordicsemi.com/bundle/ug_ppk2/page/UG/ppk/setting_up.html
and cut the solder bridge (SB40).

[quote userid="108933" url="~/f/nordic-q-a/128104/measurement-issues-with-ppk-2-on-nrf52833-dk/566268"]To use the li-po on SW9, you need a Li-Po battery connected to either J6 or P27.[/quote]

I think you misread what I meant:
If the ppk is the source and SW9 is set to lipo or usb, the led now draws more current / is brighter

Source Mode Ampere Meter Mode

Tobias

RE: Measurement issues with PPK 2 on nrf52833 dk

Kazi Afroza Sultana — Tue, 12 May 2026 13:34:08 GMT

Hello,

After reading the description of your case, I think that the issue is not related to PPK; it's the way you are measuring.

The default setting of the nRF power source is VDD. To use the li-po on SW9, you need a Li-Po battery connected to either J6 or P27. In that position, the nRF52833's high-voltage regulator is supplied directly from the Li-Po battery connector.

Can you send me the picture of your setup?

Have you followed this guideline Setting up the Power Profiler Kit II while setting the DK for measuring current?

Thanks.

KZI