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STM32WB35 Higher than expected power consumption in stop mode



I have a project with a STM32WB35. The VddUSB is powered by an extra regulator. The VddRF is using the internal power path. Vdd and VddA are powered from a 1V8 regulator.
I am using an external 32MHz oscillator and a 32,786kHz oscillator for the RTCC.

The PCB it is on is custom made for the project. At the moment, I can not rule out a design mistake but from my probing thus far I can not find any.
I am trying to measure the quiescent of the PCB which at the moment is too high for my liking ~55uA when expected in stop2mode it should be 2 - 3uA.

I first bring the CPU2 in stop2mode and then the CPU1 in stop2mode. The main oscillator stops (checked with probe) and the RTCC oscillator continues to run.

The SMPS is in bypass mode ( which also should anyhow be the effective mode at the voltage at the Vdd is at 1V8 ). And the voltage that I measure at VddRF is ~1V0.

The program I am trying to run is a simple blinky that after a while goes into sleep / stop mode. Right now I am at the proof of concept stage with no complicated code running at the background.
I am using STMCubeIDE to program the microcontroller.

Up to now, to be honest, I have not understood yet if the Radio Module is a separate module or not ( from some advertisement X-Ray photos on ST website it seems that it might be indeed a SoC but many grains of salt there ).
I am leaning more to the scenario of not closing some peripheral at the moment which is consuming power rather than having a problem with the design of the PCB.

I am also trying to find an example of how to power-off all the peripherals, stop clock even to the GPIOs ( set them to analog etc... ).

I have pull-ups and pull-downs on the JTAG pins but I have repurposed them, so I am not suspecting any leak current from there. I am also tested for that with a multimeter (current and voltage ) and that also seems to be the case.

I am currently reading though the datasheets, but hey if anybody knows the answer or is suspecting anything, I wouldn´t mind hearing it ( or better said reading it ).
Right now my suspicion for the extra consumption is the Radio module, of which I do not know yet if I can disable the internal LDO or not.

Thanks in advance for any answers,


And to end any doubt, I removed the microcontroller to be certain, leaving only some transistor translators, LDO and some other stuff.

Without the microcontroller I get a current consumption of 100 - 110nA, so something something is staying alive in the micro.
And no it´s not the ground current of the LDO that suddenly shoots up when the microcontroller is connected, neither the datasheets
support that, not measurements with (static though) load.

So it is something something microcontroller something without a doubt now.

- Lefteris

So, it ends up that this post is another RTFM public announcement...

Vddrf MUST be connected to Vdd at all times. I leave this post for future reference for others  ::)

- Lefteris



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