70% boards get fried when trying to program

[Kemsa]

Hello community,

I have thiss board, the first one  I'm designing from scratch on stm32 platform. I am able to connect and program just fine to some of the MCUs, but for the vast majority, the chip somehow gets fried before I can program it: I can't detect the MCU at all with cube programmer.

Here is the relevant part of the schematic I'm using, is there anything I should add? This board connects to a programming board which is in turn connected to the ST link.

MCU is STM32G0B1

[waclawek.jan]

Make sure grounds between programmer and target are safely connected, before connecting any other signal, including power.

JW

[Javier1]

what @waclawek.jan  said, also check if youre applying more than 3.3 / 5 v  to the gpios.

Most times this happened to me was because of isulated power supply and then i happily connected the Oscilloscope ground or my laptop ground *trough stlink

[Kemsa]

We have a power switch on programming board. We make sure it's switched off before plugging the board. That should be enough? The STlink however is still powered then, but I believe it's OK since it doesn't provide any power?

[Kemsa]

What do you mean by "insulated power supply"? Like a battery or something not connected to general ground?

Also I don't think I go anywhere above 3.3V as I have an LDO before supply, and it's not fried. I have some doubts howwever on it's reliability...It could be that it's not good quality (I had to make tradeoffs regarding size) and produces some voltage spikes.

[LCE]

What's the STM32 package?

Are you 100% sure about the soldering quality, also of the LDO?

PB15 directly connected to GND looks dangerous, what's that pin ? Maybe try to get 1k between pin and GND.

[Javier1]

i meant isolated sorry for the typo.

Just make sure all your GND are connected together, from your stlink(USB laptop) and from your power supply and any oscilloscope probe