2024-09-25 07:04 PM
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!
2024-09-25 08:06 PM
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.
2024-09-25 09:47 PM
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.
2024-09-26 06:36 PM
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?
2024-09-26 06:37 PM
Thank you for your answer, very beneficial.