STM32G474 UART4 RX pin pull up

KayalaSandeep · ‎2025-11-11

In STM32G474 UART4 pin no PC11(Rx) is 5 Volt tolerant . If I pull up this pin to +5V with 4.7kOhms then it will affect life or operation of microcontroller? please Suggest.

mƎALLEm · ‎2025-11-11

Hello,

According to the datasheet this pin is FT_f which means it's Five volt tolerant with Fast mode + capability.

Fast mode + pins can sustain a current of 20mA:

Doing the calculation:

5V/4.7.10-3 = 1mA -> far from the maximum allowed (20mA).

So no problem with your config.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

View solution in original post

mƎALLEm · ‎2025-11-11

Hello,

According to the datasheet this pin is FT_f which means it's Five volt tolerant with Fast mode + capability.

Fast mode + pins can sustain a current of 20mA:

Doing the calculation:

5V/4.7.10-3 = 1mA -> far from the maximum allowed (20mA).

So no problem with your config.

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

KayalaSandeep · ‎2025-11-11

Thanks for the reply. But I did the exact process two times in both the cases my controller stopped working and overheating two time what could be possible reason. First time UART Tx and Rx pins are shorted and second time entire microcontroller is overheating . Please explain what could be the possible reasons

Andrew Neil · ‎2025-11-11

That's a new question - so please start a new thread.

You can post a link here to your new thread so that people can follow; also in the new thread link back to here for reference.

You will need to give more details of your hardware and environment:

How to write your question to maximize your chances to find a solution

A complex system that works is invariably found to have evolved from a simple system that worked.
A complex system designed from scratch never works and cannot be patched up to make it work.

mƎALLEm · ‎2025-11-11

Possible reasons:

- Wrong pull-up resistor value. Measure your pull-up resistor. 4.7k?

- The resistor is not pulled up to 5V but to a voltage level more than that. So check again that voltage.

- Or something else not related to that pull-up. How did you conclude the chip is heating after adding this pull-up? it could be heating from another reason!

To give better visibility on the answered topics, please click on "Accept as Solution" on the reply which solved your issue or answered your question.

James_Walker · ‎2025-11-11

Yes — PC11 (UART4_RX) on the STM32G474 is 5 V tolerant, so pulling it up to +5 V through a 4.7 kΩ resistor is electrically safe. It won’t damage or shorten the MCU’s life as long as the pin is configured as a digital input (not analog or output).

Just make sure:

VDD of the MCU is powered when 5 V is present on that pin (to avoid latch-up).
Don’t exceed 5 V — keep it within spec (check the datasheet “5 V tolerant I/O” section).

So yes, your setup is fine and won’t affect normal operation or lifespan.