STM32F103VGT6 Channel 4 ADC acquisition pin malfunction

[DLRJ]

①Fault Phenomenon: The fourth physical output core acquisition pin is faulty. Without any external connections, the voltage at the CPU pin measures around 4.3V, whereas it should normally be 0V. This also causes the operational amplifier chips connected to it to experience overvoltage. After removing the external connected components and chips, the CPU pin still has floating voltage, and the physical output core reads floating values. Replacing the external operational amplifier chips does not resolve the fault. After replacing the CPU chip, the fault is eliminated.

②Fault Location: The U8 pin (pin on page 3) is damaged, causing overvoltage to the external op-amps (IC16, IC15) and itself exhibiting floating voltage, which leads to incorrect data acquisition in the physical output core. Meanwhile, the other four physical output core acquisition functions remain normal; only the PA3 channel is damaged.

[TDK]

The chip can't supply more voltage than VDD. That is not physically possible.

It sounds like you have other hardware issues. What hardware even is this?

[DLRJ]

This chip is used on Shenzhen Metro Line 1.

The email ststes it should not exceed VDD.

Our fault is that one channel has failed.

ls there a misunderstanding in the understanding？

The ADC operates by converting a 0-2.5V 

analog input into a digital signal ranging from 0 to 4095.

After the ADC channel fails，the digital signal remains unchanged

despite variations in the external input，resulting in an error.

[DLRJ]

This chip is used on Shenzhen Metro Line 1.

The email ststes it should not exceed VDD.

Our fault is that one channel has failed.

ls there a misunderstanding in the understanding？

The ADC operates by converting a 0-2.5V 

analog input into a digital signal ranging from 0 to 4095.

After the ADC channel fails，the digital signal remains unchanged

despite variations in the external input，resulting in an error.

[TDK]

The chip cannot produce a higher voltage than VDD. If a pin is at 4.3 V, it is due to an external power source. It is not a fault of the chip.

There is not nearly enough information to diagnose this further.

[Ozone]

If a pin statically exhibits a voltage 700mV beyond the rated maximum, it is most probably irreversibly damaged.

Some external circuitry has probably injected an EMI spike, and now protective circuitry on the GPIO input is blown.

Most probably, the only remedy is to replace the MCU, and review & improve the EMI protection measures.