STM32H757 MCU at VCAP pin 0 volt

[BerkayC]

Hi 

I working on a STM32H757BIT6 custom board. I try to take a referance with riverdi TouchGFX. This is my power connection with an mcu. 

                      

Additionally, I have measured the voltage on the VLXSMPS pin and found it to be approximately 1.01V. This pin is not connected to any external voltage source, indicating that the internal SMPS is likely enabled.

For the power configuration, I am using a 2.2µH inductor as recommended in the reference manual. However, the VCAP pin only outputs 0.17V, which is significantly lower than the expected ~1.2V. This suggests that the internal regulator is not functioning correctly.

I programmed the Riverdi development board itself with a basic LED blink application. The programming was completed successfully. However, when I attempted to reprogram the board or reconnect via the ST-LINK, I encountered the same issue as with my custom board:
"No device found on target."

I then checked the VCAP pins on the Riverdi development board and observed 0V, which confirms that the core of the microcontroller is not running.

Thank you for your support and assistance.

[TDK]

Verify part orientation. Show full schematic.

[mƎALLEm]

Hello,

Not sure what is the power configuration of the Riverdi board? SMPS?

If so, this is the hardware required for the direct SMPS (RM0399 rev4/Figure 22):

In that case, VDDLDO is connected to VFBSMPS and not to VDD.

So please check all that hardware section.

Hope that helps.

[BerkayC]

I connect the VFBSPMS pin to VCap pin and it is programing. The VDDLDO pin is currently connected directly to VDD and can not cut the this connection.

Although the device can still be programmed and enters the while(1) loop during debugging, it consistently draws approximately 27 mA of current. However, the LED does not blink as expected. 

[BerkayC]

This is my full schametic of the MCU

[mƎALLEm]

You need to follow the exact hardware schematic I provided for SMPS, otherwise there will be issues in the power. 

[MHoll.2]

As  mƎALLEm  has explaind Yo have to follow the  indication in the reference Manual.

If You want to use the "simple" LDO supply mode, You have to connect VDDSMPS and VFBSMPS to GND.

Any thing else can damage the MCU.

[BerkayC]

It appears that the chip itself is entering the protection mode . When I connect the BOOT pin to VDD before powering up the board, the device becomes accessible via the STM32 programmer. While the BOOT pin remains connected to VDD, I am able to perform a full chip erase successfully.

However, after powering the board down and then back up, I observe that the voltage on the VCAP pin stabilizes around 1.1 V.

Notably, Riverdi seems to be experiencing a similar issue with this behavior.

Thanks for the help

[MHoll.2 · Accepted solution]

This are two things:

1) You have to correct the connection of VDDSMPS and VFBSMPS.

2) You have to tell the MCU that You want to use the LDO supply by setting PowerSource to PWR_LDO_SUPPLY under RCC ( I know, not very intuitive).

[BerkayC]

This solution is working. I believe the issue was caused by an incorrect configuration in CubeMX, which triggered the MCU to enter protection mode.

Thank you very much for your assistance.