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Lyu.1
Senior
September 26, 2024
Question

GPIO pin transient load current capacity

  • September 26, 2024
  • 4 replies
  • 1813 views

Master:

Platform: stm32G070cb
Quesion:
The MCU pin is driven through a 100R resistor to drive an N-channel MOS transistor (2N7002, Ciss < 50pF).
When the pin is given a high output, the starting transient current peak approximates I = 3.3V / 100R = 33mA,
This will exceed the limit values in the table below, this design will be unreasonable, am I correct in my understanding?

Thank you very much!

q.png

 

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4 replies

TDK
September 26, 2024

Correct. The drivers are self-limiting, so you won't typically damage the chip, but it will fail to deliver 33 mA. Using a transistor to switch the current directly from the rail would be the better design.

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Lyu.1
Lyu.1Author
Senior
September 27, 2024

Thank you for your answer, very beneficial.

MasterT
Lead II
September 26, 2024

Current limits in table for continious condition, means  >10 years in wide temperature range. 

For short transient x3-5 times overload is o'k.

There is another table 49 p.65 that specify drive condition with 50 pF load, so no worry. Only rise/ fall time stretched, depends on application if it's important.

STM32G070CB GPIO.png

Lyu.1
Lyu.1Author
Senior
September 27, 2024

Thank you for your answer.

"For short transient x3-5 times overload is o'k." Is there any documentation for this? Or a potential default design?