STM32H7B0 voltage scaling problem

[FeherAron]

Hello everyone!

I've designed a PCB around the STM32H7B0 MCU (I've attached a screenshot of the relevant part of the schematic) for audio signal processing.  

I wanted to use the maximum clock frequency of 280MHz, but this requires the use of Power Regulator Voltage Scale 0. And here is the problem: regardless of whether I use an internal or external clock source, as soon as I change the voltage scale from 3 to anything of higher performance, the MCU hangs when it comes to the oscillator/voltage scale switching. After that, I can't even program it using the usual means. I have to manually reset the MCU and completely erase the flash.

I don't think it is a crystal problem since it works below 88MHz. 

I did not paste any code since the default generated HAL code has this behaviour.

Could you please help me figure out why I can't use the high-performance modes? Is this a CubeMX configuration problem ,or something that I'm missing? I also did not find anything relevant in the errata.

MCU schematic part

[FeherAron]

So, after a few weeks of debugging and document reading, I've partially solved my problem.
I probably got the hiccups or something because I've placed 2.2nF caps at the VCAP pins. The datasheet clearly states 2.2uF caps. After replacing those, I could suddenly program the MCU, which did not freeze. Now, I can test my audio effects.

I say partially solved because I can only program the MCU. For some reason, as soon as I try to debug, the connection with the target is lost - yes, the trace async sw pins are enabled in CubeMX. This must suffice for now, but I'll also try to solve the second issue.