STM32L412RBT, IO damaged very easily?

[taz1000]

Hi,

I'm using STM32L412RBT, LQFP64pin.

As the attached schematic, we are using some GPIO's as BTN inputs.

But, unfortunately, the GPIO got damaged very easily without special reason.

The pin voltage stuck at 1.0 ~ 1.7V when the button is not pressed.

We assembled 10 boards, and 3MCUs has this problem.

We had used the similar schematic with STM32F201, STM32F767, and so on.

But, this is the first time we're using STM32L412RBT and now we have problem.

As I know, STM32L412 is one of most recently released MCU from ST.

Is there any known issue regarding to GPIO damage ?

Or is there special design guide for STM32L412 ?

* If you want, I can send one or two MCUs for your analysis.

* If there is any known issue, I need to change the MCU to a compatible one.

 * IO damage occurs on MCU RESET input pins also.

VDD is 3.3V.

Best Regards,

Danny

[davidle.ee9]

Please share to know what is the final ans. if possible please!

[S.Ma]

The external pull-ups are not needed as they can be activated at GPIO levels.

If the internal pull-down is activated, the voltage might not be 3.3V

Reverse the reasoning, for the pin as output and in the debugger manually set to 1 and 0 and check the output voltage.

Unless the PCB making pick and place machine has issues and creates a damaging ESD overspec shock, it might be something else, unless there is something mentionned in the errata sheet...

[taz1000]

I had changed the MCU to STM32F4xx for higher performance and memory sizes.

( no change in HW , only MCU is changed.)

After changing the MCU, I don't have the issue any more.

[S.Ma]

I smell the button is populated with wrong orientation. Check the button by disconectting the 100 Ohm.

Also, with internal pull up in the MCU, the external 10k is not needed.

With SW debouncing, the 100nF capacitor and 100 Ohm resistor are optional as well.