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Pulling up a GPIO to 9v

Question asked by Robison.Don.002 on Apr 1, 2017

I have the STM32F4 discovery board.  I want to use the GPIO to drive the gate of a power MOSFET up to 9V.  Everything works well with push/pull output, then I configured the pin for open drain output, and add the resistors and 9V supply.  I pulled the pin up to 9volts with 10kohm and down to ground with 1Mohm.  The output looks fine when it's low, but when I try to toggle it high it just goes up like 0.1v but is still low.

 

I was looking at the output more, and I noticed there are protection diodes on the I/O pins.  I think this might be my problem.  Is it even possible to pull up the output pin above 3v when configured open drain?  What is the max limit? 

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