Unable to Connect to a Custom H725RGV6 Board

[Leonana69]

Hi all, recently I made a board with H725RGV6, but when I tried to flash a test firmware for the first time, I got " Error: No STM32 target found! If your product embeds Debug Authentication, please perform a discovery using Debug Authentication" from STM32CubeProgrammer (I'm using STLink V2). 

I measured the power supply and VCAP, VDD looks good at 3.1v, but the VCAP is only 100mv which is not correct. I also tried to remove the third 2.2uF for VCAP and connect PIN66 to PIN49, so VCAP is around 80mv.

- I've checked the orientation.

- I soldered the chip with a 700F heat gun and tried 3 chips in total.

- Updates: I tried to supply 1.2V to VCAP, then I can connect to the chip. But why? Shouldn't the chip have internal LDO?

Below is the power supply part schematic. Does any one have any suggestions?

[tjaekel]

Just thinking...

You have a chip with SMPS - but you do not use it (VDDSMPS is GND). Not sure, I would expect: when a chip with SMPS (the Q version) - provide the 2.2microH coil and let "use" SMPS (if it is not an LDO bonded chip version).

Another issue could be:
What is the header pinout for your debugger?
The debugger wants to see the VDD of the target: if you do not provide VDD on debug header - the debugger might "think": "there is not a target connected. And debugger needs also VDD from target in order to "adapt" the debug voltage levels. Without VDD to debugger - it fails.

My debug header for ST-LINK looks like this:

If the debugger does not find VDD (or the GND via this 100R) - it might assume the target is not connected.

[Leonana69]

Hi tjaekel, thanks for your reply.

1. In the AN5419, it says "On STM32H723/733, VDDLDO is not available on a pin/ball. It is internally connected to VDD". So I assume it's the same for the STM32H725RGV6 since there is no VDDLDO pin on the chip. I found most people don't use the SMPS and they all work fine, so I also didn't use it.

2. I've provided the VDD for the debugger. However, the main problem seems to be the chip not booting up correctly since the VCAP is low.

[Leonana69 · Accepted solution]

Finally found the issue, the H725RGV6 package doesn't include the internal LDO.