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Optimal way to drive Pfets with 3.3V signal

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jonroger:
You need to switch the MCU between "high impedance" and "ground", not the usual "3.3V" and ground.   I've done this on a 5V tolerant MCU and it works well.

Zero999:

--- Quote from: 3dgeo on October 31, 2019, 10:55:58 pm ---Thank you for your replies.

Yes, level shifter would do the trick, tho they are more expensive then darlington arrays (8.5ct).
--- End quote ---
There are cheaper 74HCT series parts which will run off 5V and accept 3.3V logic levels. Try the 74HCT14, which is inverting, so a P-channel MOSFET will turn on, when the input is high. If it must be non-inverting, then there's the 74HCT241 or 74HCT08 AND gate.

3dgeo:

--- Quote from: jonroger on November 01, 2019, 10:34:52 pm ---You need to switch the MCU between "high impedance" and "ground", not the usual "3.3V" and ground.   I've done this on a 5V tolerant MCU and it works well.

--- End quote ---

If you mean open-drain output then yes, this will work, this is exactly how darlington transistor chip I planned to use works. STM32 IOs has open drain, so yeeey, no extra chip :)

Thanks!!!!! :)


--- Quote from: Zero999 on November 01, 2019, 11:45:03 pm ---There are cheaper 74HCT series parts which will run off 5V and accept 3.3V logic levels. Try the 74HCT14, which is inverting, so a P-channel MOSFET will turn on, when the input is high. If it must be non-inverting, then there's the 74HCT241 or 74HCT08 AND gate.

--- End quote ---

Good suggestion, only problem that those are HEX and I have 7 fets  :-\

Zero999:

--- Quote from: 3dgeo on November 02, 2019, 06:46:37 pm ---Good suggestion, only problem that those are HEX and I have 7 fets  :-\

--- End quote ---
You didn't click on all of the links. The 74HCT241 is octal.
https://assets.nexperia.com/documents/data-sheet/74HC_HCT241.pdf

The 74HCT1G14 is a single gate package, so you could also use that in addition to the 74HCT14, but it's not a very elegant solution.
https://assets.nexperia.com/documents/data-sheet/74HC_HCT1G14.pdf

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