Open collector microcontroller output SEEK HELP!

Questions on other types of hardware and getting it talking to the ARM CPU
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Joined: Fri Nov 18, 2016 7:03 am

Open collector microcontroller output SEEK HELP!

Postby Mattle » Fri Nov 18, 2016 7:09 am

I am building the following circuit, in order to control the P channel MOSFET as a high side switch for my load.

The input of this circuit will be from a microcontroller (maybe an STM32F103), and I was planning to use the output pin, in open collector mode.
STM32F103 PDF:
Will this work? Please note that I am pulling up the pin at 12V.

I know that in other circumstances it would work, but in a microcontroller, will the output handle the 12V? When in open collector, are the ESD diodes disconnected?

And if it works, how do you handle the initialization of the pin, (after reset, before configured as an open collector pin).

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Re: Open collector microcontroller output SEEK HELP!

Postby basicchip » Fri Nov 18, 2016 9:18 pm

That device has GPIOs that can be configured as both push-pull and open-drain. But as these are not true open drain, they most likely will latchup when pulled up to 12V. A BAD thing.

So you need to buffer that output, either with a transistor, or FET driver.

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