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I am using stm32f303rbt6 MCU, And I am using UART &USART, while working with this i found that some UART & USART are 5 volt tollernt, But Tx pin of these UARTs are not providing 5volt, they only provide 3.3 volt, Then how can it become 5 volt tollrent,

Kavin
Associate

‎2023-05-13 10:06 AM

Can anyone explain it to me?

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Karl Yamashita
Lead III

‎2023-05-13 11:15 AM

The GPIO's that are 5v tolerant have clamping diodes which won't let the voltage go above VDD.

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Tesla DeLorean
Guru

‎2023-05-14 07:17 AM

>>Can anyone explain it to me?

Probably relates to the dictionary definition of "tolerant", you should look that up.

Chances are that a 3.3V you're well into the VIN-HIGH threshold for 5V systems

You could try using the pin in Open-Drain, with an external pull-up to 5V

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