5 volt open drain

[pietrodicastri]

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

[stevenjohnson]

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.

[apanecatl]

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.

[pietrodicastri]

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

[egoodii]

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