STM32H7 Board - "Target Not Found" - VCAP (2.7V) and VDD drop

[Matheus_Markies]

Hi everyone,

I am bringing up a custom board based on the STM32H743VIT6. I am trying to connect via ST-Link (SWD), but I am getting the standard "Can not connect to target" error in STM32CubeProgrammer.

The Setup:

• MCU: STM32H743VIT6
• Debugger: ST-Link
• Interface: SWD (SWDIO, SWCLK, GND, 3.3V detected)
• Power Supply: External 3.3V. Board voltage source to provide the necessary power for the system, something that ST-Link alone cannot do.

The Problem: After failing to connect, I probed the power pins and found abnormal values:

• VCAP Pin: I measured 2.7 V on the VCAP pin. As I understand it, VCAP corresponds to the internal LDO output for VCORE and should normally be around 1.2 V. Does a reading of 2.7 V indicate an internal short circuit to VDD or a blown LDO?
• VDD Drop (Pin 75): On Pin 75 (VDD input), I have a known bad solder connection (trace compromised). I measured 2.3V on this pin.

Question: Since the other VDD pins are correctly supplied with 3.3V, shouldn't the internal silicon power mesh maintain Pin 75 at ~3.3V? Or does a drop to 2.3V confirm that the chip is not being properly energized internally?

Schematic: https://github.com/MatheusMarkies/Route-ECU-Hardware.git

What I've checked:

• NRST pin is high (3.3V).
• SWDIO/SWCLK connectivity to the header seems okay.

Has anyone experienced VCAP rising to ~2.7V? Does this imply the chip is dead?

[TDK]

VCAP going to 2.7V suggests a hardware issue with the board. Is there a bulk capacitor on 3.3V somewhere? Otherwise the schematic looks okay.

Double check the VCAP traces to ensure nothing is shorted.

The chip may be damaged, but if there's a hardware issue and the problem is fixed, the chip may be able to recover.

> I have a known bad solder connection (trace compromised). I measured 2.3V on this pin.

All VDD pins need to be supplied externally. The internal network will try to maintain this, but it's not guaranteed.

 

Perhaps you have it misoriented. If text is oriented from left to right as you would read it, pin 1 is on the bottom left.