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STM32L0xx saw tooth current in permanent run mode

Associate III


if I never call any wfi / wfe and run my stm32l0xx mcu in permanent run mode, I got a sawtooth shaped consumption current.

In normal mode, where I call wfi, this is not a issue, but I'm curious.

Any ideas where this comes from?

Thanks & best regards



> Any ideas where this comes from?

This is how the internal power regulator (which generates core voltage from VDD) works.


Muhammed Güler
Senior III

If the voltage is stable, fluctuating current is not a problem for most applications. If there are similar fluctuations in the supply voltage, you should review your power distribution network. You can stack capacitors next to the pins that cause current fluctuations.

Lead II

What I find surprising is how slow the sawtooth is. I can't imagine any switching power-supply doing one pulse every 50 seconds!

What it could be is aliasing of a switching-power-supply with the sampling process of your current measurement - assuming that your measurement might suffer from aliasing. (Which is a big assumption - can you expand on precisely how you are measuring the current e.g. what is the sampling-mode of your 'scope; are you measuring the voltage-drop across a resistor, or using a current-transformer or what.)

Now the stm32L0xx has, I think, an internal linear LDO voltage-regulator for the core - so I wouldn't expect that to be switching and causing current-gulps. But if your external circuitry has a switching regulator to supply Vdd, then that could be what your measurement sampling process is beating against.

Can you say precisely which stm32L0xx it is?

I have used stm32l496 which has built-in a linear regulator, with the option to attach an external switcher. I think TI pioneered built-in switchers for their msp430 but ST might have them as well now.

Or it could be something to do with your code. If your code does different things over time, it is possible that some of those things use more current than others.

Hope this helps,