2.2V on VCAP pin on STM32H747BIT6

[bacaneriaslocas]

Hi, I started working on my own dev board for a flight computer based on the STM32H747BIT6.

At first, I struggled a bit to connect the board to the computer, only managing to do so using the hot plug mode in order to get some info from the microcontroller. My problem comes when trying to write something to the flash: it gets stuck on erasing internal memory sector 0. This means it is unable to write or modify the flash memory. Also, when I connect the board to the STM32CubeProgrammer, it shows me the flash memory, but every address is at 0, which makes sense given that I haven’t uploaded any code to the microcontroller.

I’m not really sure what this means — I’m able to read it, but not write to it.

The thing is, I started measuring the power source pins just in case I spotted something weird, and I sure did: my VCAP pins are at 2.2V, which is strange because they should be at 1.2V according to the internal LDO regulator.

My guess is that this may be the source of the problem — an incorrect power source for the flash memory — but I’m not sure.
Here I attach my squematic.

[bacaneriaslocas]

Hi, Sorry for the lack of update, I have been working on the solution of the problem, my last conclusion is that the chip it's fake.

As I bought it from aliexpress, it is probable that the chip it is not 100% original. 

Other clue that lead me to this conclusion is that when trying to conect to the chip through st link utility is that it shows me a flash storage of 25megabits which as far as I know, it only has 2 megabits.

[mƎALLEm]

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@bacaneriaslocas wrote:

Hi, Sorry for the lack of update, I have been working on the solution of the problem, my last conclusion is that the chip it's fake.

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Unlikely it's a fake chip especially for STM32H7 .. You may damaged your chip by an incorrect hardware ..

[bacaneriaslocas]

But what's the explanation of the 25mgb being shown?

[mƎALLEm]

Frankly I don't know.. To answer that question I need to have that device at my hands and handle it which is not possible. May be you need to contact your local sales for that.

[AScha.3]

Just a simple question: you write : STM32H747BIT6

but you use only LDO - why?  afaik it should be using smps + LDO (for max speed)

and vcap 2.2 uF ....not your many caps...

Try to change the vcap and check (if cpu still alive...).

And no, its not a fake. Maybe its a damaged cpu now.

[bacaneriaslocas]

"but you use only LDO - why?  afaik it should be using smps + LDO (for max speed)"
Correct me if I´m wrong but I think for the max speed is only necesary the LDO, but I´m not sure.

I also tried removing the VCAP capacitors leaving only two but no diferent result.

Do you think it could be worth trying to bypas the voltaje regulators and supling the 1.2V externally to se if the cpu is okey?

[AScha.3]

That should work....but is just a experimental attempt. LDO input should be...same, 1.2V .

vcap IS the core voltage.

Try with watching the current, while rising from 0 to 1.2V ; if current goes > 200mA ...forget it.

If lower...maybe still ok. Should connect then , VDD at 3v3, to st-link. Then you know...

[bacaneriaslocas · Accepted solution]

FOUND THE SOLUTION
one pin of vddldo was not properly solder
Thanks everybody for your time and atention