Power configuration issues

[MNico.2]

Hello everyone,

I've just realized a PCB using STM32H7A3 micro. But at second step I already fell.

I've my system powered up at 3.3V from an external circuit. The quality seems to be good.

I've tried to program the micro using STlink through a SWD port. The result is "No device found on target ".

I'm sure the setup works as I used it for programming the devlopement board STM32H745I-DISCO. In that case I've had no problem.

I've checked the signals on the PCB as far as reachable:

• Reset is pulled high
• Boot0 is pulled low
• VCC is stable at 3.3V and appears at all desired pins of the board
• GND is connected to all the necessary pins
• VDDA and VDDS are connected to 2,5V and GND
• PDR_ON is connected 3.3V

I suppose could be a matter of power supply so I started checking my configuration.

Here's my condition. I use an external regulator and I want to use only the internal LDO:

What's strange to me is that I expect to read something around 1,2V across the capacitors

connected to VCAP while actually there's nothing on it. So I wonder the LDO regulator

isn't working.

Does anyone have a suggestion on how to proceed?

Kind regards.

Matteo

[MNico.2]

Found out the issue.

It's as been already explained by the good Adam BERLINGER in this topic.

https://community.st.com/s/article/FAQ-Unable-to-connect-to-STM32H7-devices

The strange thing is that I've never programmed the chip before though.

In any case following his procedure I've been able to erase the chip and

connect properly.