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I'm using STM32H750VBT6 and my template code is generated by CubeMX. I don't use external RCC but low speed clock crystal.

In CubeMX at RCC I clicked on parameter settings tab. I then changed the value SupplySource from PWR_LDO_SUPPLY to PWR_EXTERNAL_SOURCE_SUPPLY.

After changing this parameter and programming my micro controller, it then turned on. But after the first turn off my MCU never turned on.

It is not heated but has no any response to programmer too. I used an external crystal, but no response.

I used program under reset by holding NRST pin low and high during programming start witch didn't help.

Error is: Can not connect to target.

By looking into STM32H7 PWR from ST, I found that for external source or bypass LDO, voltage should be connected to VCAP.

So I connected a 3.3V to VCAP but my MCU is heated in this mode and doesn't response. (I tested VBat too.)

Where is external supply source pin? What's LDO bypass? I don't see some pin like VDDUSB33 or VDDUSB50 pins in this package (LQFP100) too. My MCU seems to have only VDD, VDDA, VSS, VCap, VBat, NRST.

How can this be solved?

JYelton
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Ghm y
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  • This is hard to tell without schematics. Generally, using an internal LDO is the "special snowflake" scenario and finding reference design for the case without one should be straight-forward? – Lundin May 18 '22 at 09:57
  • In my schematic, I used two 2.2uf caps on VCAP pins, and VDD connected to 3.3v, and VDDA to filtered 3.3v, VBat to a battery and VSS to Gnd. Vref+ is floating(connected to internal VRefBuff) ,NRST is floating, and Boot0 is pulled down by a 4.7k resistor. – Ghm y May 18 '22 at 10:06
  • Why would you connect the battery voltage to the MCU if you wish to move away from internal to external supply? – Lundin May 18 '22 at 10:08
  • I don't want to use external sup. I only tested this parameter and had no info about it. I will change it back if it turns on. – Ghm y May 18 '22 at 10:11
  • It's not clear why you thought that "external clock crystal" would be related to "external power regulator". Or why you think the RCC is an alternative to a clock crystal. There may be an R-C circuit (or even two) among your clock options, but "RCC" is not a clock option, it's the "Resets and Clocks Controller" peripheral inside your chip that controls clock distribution, sleep, etc. You have to use it no matter what your clock source is. – Ben Voigt May 18 '22 at 21:54

1 Answers1

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The RCC settings are done runtime, so it would have been saved if you had managed to erase the flash or reprogram it, before the old and incorrect code starts to run.

But, VCAP is the core voltage input, so MCU core was destroyed with overvoltage by connecting 3.3V to VCAP, so you cannot solve the problem any more without replacing the MCU with a working one.

Justme
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  • Hi. Yes your right. I had to connect VCap to 1.2 v core voltage instead of 3.3v(no response and heating.) Any way I tested this and MCU began to run by 1.2v and returned back. I had to look at AN5307(SMPS and stm32h7) instead of PWR. Thank you for your answer. – Ghm y May 18 '22 at 11:22