STM32 doesn't power on fully with eurorack power supply

Ive been using an STM32L412 for a project and had some boards made for it, however when I connect it to a eurorack power supply the module freezes on power on. Ive seen elsewhere on this forum this can happen with STM32s and some eurorack modules based on them when powered from eurorack power supplies. I understand this is something to do with the reset and the time it takes to reach the operating voltage, but that’s all I know.

Maybe someone can tell me - is there a work-around for this problem? I would really like to salvage what I have made already, hopefully there is a way to compensate for it on the chip, or a component value change? if anyone can point me to some resources where I can learn more, I’d really appreciate it


this shows the MCU, power and voltage reference

it works fine on a bench power supply, but when it’s connected in my rack, it’s as if the program has frozen - the PWM for the LEDs work, it makes sound but the ADCs don’t work. Turning the module off a few times jogs it into life

I don’t think this is the problem described in the other thread (which causes the MCU to not start at all).

I find it a bit strange that you’re powering the analog section of your MCU with the output of an op-amp. Are you sure it delivers enough current? Have you tried powering it with the same supply voltage as the digital section, or with another regulator?

ahh, yes that is a mistake - I was thinking that pin was only a reference. Fortunately it seems like it functions OK and the same thing happens when i connect the 3.3v regulator to the Vdda/Vref