NUCLEO-H723ZG OVRCR LED turns ON only when JP4 (VDD_MCU) is installed

[apmapprojectev]

Hello everyone,

I am facing a persistent OVRCR (LD6) over-current indication on a NUCLEO-H723ZG board and would appreciate guidance.

Board behavior

Powering the board via CN1 (ST-LINK USB) only

No external connections: no peripherals, no wires, no common ground, no shields

Power source selector JP2 set to STLINK

Observations

JP4 removed (VDD_MCU / IDD link open):

LD6 (OVRCR) OFF

LD5 solid green

ST-LINK enumerates correctly on PC

E5V ≈ 5 V

3V3 ≈ 3.2–3.3 V

JP4 installed:

LD6 (OVRCR) turns RED immediately

LD5 flickers faintly

USB power switch (U2 near CN1) starts heating

Board does not stay powered

Current measurement across JP4:

Measured by replacing JP4 with a multimeter (DC current mode)

Target domain draws ~1 A

This happens regardless of JP5 position (VB–VDD or VDD–3V3)

Resistance measurements (USB unplugged):

With JP4 installed:

3V3 → GND ≈ 10–60 Ω

IOREF / VBAT → GND similar range

With JP4 removed:

3V3 / IOREF / VBAT → GND ≈ 150–200 Ω

Conclusion so far

Base power system is OK

Overcurrent occurs only when the VDD_MCU domain is connected

~1 A draw is far beyond normal for a bare target MCU domain

USB power switch correctly enters protection (OVRCR)

Questions

What is the expected current range for the VDD_MCU domain on NUCLEO-H723ZG at power-up?

Are there any known failure modes or checks recommended when:

OVRCR triggers immediately with JP4 installed

JP5 selection does not change behavior

Is there any additional jumper or configuration that could cause this behavior, or does this indicate a fault in the target power domain?

Any insights from ST or community members would be greatly appreciated.

Thank you.

[TDK]

You should place the board on a nonconductive surface. An ESD bag will work. Putting it on cloth or fabric is probably okay but certainly increases the risk of ESD. If fabric has metallic strands in it, it could be conductive which is not good here. Don't want to short random pins together.

 

> With JP4 installed:

> 3V3 → GND ≈ 10–60 Ω

Definitely indicates hardware damage. On my board, I get 8.3 kOhm. 

With the board powered, you can see which chip heats up either using an infrared camera or your finger. If it's the STM32, you'll need to replace it. U2 getting hot is expected if there's a short somewhere else. Unlikely U2 is the culprit here.