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SWD debug failure in High voltage situation

Question asked by ningmeng.xie on May 6, 2017
Latest reply on May 6, 2017 by Jeroen3


    I am using the chip STM32F405 when developing a power converter. It is a buck converter. 

    When the input voltage is below 25V, I used the keil to debug the chip normally, and monitor the variables.


However, when the voltage is up to 40V or even more, I cannot debug any more.



The following is the SWD interface I designed



Debug hardware: STM32F0discovery working as stlink debuger

Debug target: STM32F405RGT

Debug interface: SWD


The power of the MCU is provided by standalone DC source of 3.3V.

The input voltage of the buck converter is provided by another DC source.



So, why I cannot debug the target when the input voltage is high? Is there any things I should paid attention to when designing the debug circuit in such high voltage application?