stm32h725ZGT6 custom Board Hangs

[Sakthi_Murugesan]

Hello STM32 Community,

I’m working with a custom board featuring the STM32H725ZGT6, and I’m encountering some issues I hope you can help with. Out of the 10 boards I've assembled, 7 are functioning perfectly. However, on a few boards, the MCU isn’t being detected in STM32Cube Programmer. When it does get detected, I receive the following error (screenshots attached).

To troubleshoot, I’ve attempted the following:

• Reflowed the MCU with hot air and checked/reballed the pins
• Tested the MCU on another working board (still facing the same detection issue)
• Replaced the MCU with a new one on the problematic board (issue persists)

Has anyone experienced similar issues or have suggestions on what might be causing this inconsistency? Any guidance would be greatly appreciated!

[SofLit]

Hello,

Review your schematics first, mainly VCAP capacitors:

[Andrew Neil]

Check against AN5419, Getting started with STM32H723/733, STM32H725/735 and STM32H730 Value Line hardware development:

https://www.st.com/resource/en/application_note/an5419-getting-started-with-stm32h723733-stm32h725735-and-stm32h730-value-line-hardware-development-stmicroelectronics.pdf

Also check for other app notes:

https://www.st.com/en/microcontrollers-microprocessors/stm32h725zg.html#documentation

[genesis78]

I'm having a similar problem with STM32H725RGV6s. I have found that on the boards that don't work the voltage at the VCAP pins is 0.12V, when it is supposed to be in the range of 1.1-1.3V. This is the post I've opened in case you are interested in cross-referencing problems or in case a solution appears: https://community.st.com/t5/stm32-mcus-products/issue-with-vcap-voltage/td-p/740895

[Tesla DeLorean]

Focus on the pin usage, and supplies. Orientation looks Ok.

Check NETLIST for islands which aren't connected, but should be, ie mispelled naming

Check incomplete boards for continuity on the supplies.

Check pin designations on symbol vs datasheet

[Sakthi_Murugesan]

here is my design

I'm sharing my board schematic here for reference, as I’m facing a few puzzling issues with my custom board based on the STM32H725ZGT6.

Here’s a summary of what’s happening:

Here’s a summary of what’s happening:

In addition to the detection issues I previously described some of the boards that do initially work show strange behavior when I attempt to flash and run code. Here’s what I’ve observed:

1. Code Not Persisting After Power Cycle: I used J-Flash Lite to program the MCU with my hex file, and the code runs as expected. However, after a power cycle or reset, the code no longer runs.

2. STM32Cube Programmer Behavior: I connected the board to STM32Cube Programmer to investigate further. After performing a full chip erase, the memory locations filled with "YYYY". I then successfully flashed the code using STM32Cube Programmer, but once again, it wouldn’t run from memory.

3. Unexpected Power Loss: While the board was connected to STM32Cube Programmer, I noticed a strange issue: the power unexpectedly cut out, causing a "connection lost" error. After power was restored, I could no longer reconnect to the MCU in STM32Cube Programmer, and it only showed errors.

   

Has anyone else encountered similar issues or have any troubleshooting suggestions? 

[Sakthi_Murugesan]

I’ve attached my schematic above, and I’d like to share some VCAP voltage readings in case it helps diagnose the issues I’m experiencing:

• VCAP_1: 1.012V
• VCAP_2: 1.01V
• VCAP_3: Starts at 3.3V, then slowly discharges to 0V with every power cycle.

I’ve replaced this capacitor twice, but the issue persists.

Is this behavior expected, or could it be pointing to an underlying issue? Any insights would be greatly appreciated

[AScha.3]

Hi,

i see some problems :

- Why you choose a chip with smps on-chip, but dont use it at all ??

- vcap pins connected not correct :

- what is on VDD33USB ?

- whats on PDR_ON , pin 142 ?

[Sakthi_Murugesan]

- VDD33USB - 0V

- PDR_ON, pin 142 = 0.2V

[AScha.3]

So you have to:

- connect VCAP pins

- connect PDR_ON, pin 142 to -> VDD

- connect  VDD33USB to -> VDD

+

after connecting these, without power, check with DMM : VDD (3v3) --- GND has no low impedance (short)