topic Re: 5 volt open drain in Kinetis Microcontrollers

5 volt open drain

pietrodicastri — Wed, 21 Jan 2015 08:32:59 GMT

Good morning

The processor is the K64 as in the FRDM board. I need to drive a 5 Volts input logic device.

I want to use the open drain avoiding the usage of a level translator.

Is it possible to use the open drain option with the external pull up connected to 5 Volts???

Thank You

Re: 5 volt open drain

apanecatl — Wed, 21 Jan 2015 17:53:51 GMT

Well it does not work that way, the GPIO pins are only 5V tolerant when configured as inputs, this means the excess voltage going into the pin is redirected to the protection rail however when a GPIO pin is configured as an output it can only provide a maximum voltage equal to VDD.

Re: 5 volt open drain

pietrodicastri — Thu, 22 Jan 2015 06:28:48 GMT

Thank You for the support.

I wander if the open drain configuration opens the possibility for the external pull up to be tied to the 5V.

Effectively in the datasheet it is written the pull up should be tied at Vdd, in Table 1 as item VODPU.

So I don t think there is a chance.

Pietro

Re: 5 volt open drain

egoodii — Thu, 22 Jan 2015 14:15:04 GMT

As an output, there will be a diode-clamp to Vdd.

Re: 5 volt open drain

stevenjohnson — Mon, 11 Apr 2016 15:06:01 GMT

I have the same question but using a K20, could the problem be tackled this way:

1. Put a pull up to 5V

2. Setup the Port Pin as Output/Open drain, Write 0 to the Output bit.

3. To drive a 5V High, change the direction to an input.

4. To drive a 0V Low, change the direction to an output. (The 0 is still in the Output bit, so the port pulls low)

Control the "output" by toggling the direction and not the Data output bit.