if I control the current into a pin configured as a open drain on a K65 micro how much higher can i pull this pin than VDD?

[jasonlarson]

I have a k65 micro that is powered from 1.8v and I have a pin configured as a open drain. I have a couple devices powered from 3.3v and would like to have the K65 pin pulled to 3.3v even though the micro is powered from 1.8v. I'm thinking if I keep the current under a few micro amps it should not cause a problem but want to verify?

[Robin_Shen]

These Pseudo Open drain pins can not be pull up to 3.3v when the MCU is powerd from 1.8v.
These Pseudo Open drain pins are only designed to drive to VDD (between 1.71 and 3.6V) even it is enabled as open drain, that is due to its hardware implementation. If it is pulled too high, the internal protection would be active and limit the output voltage.

workaround

On a pin that has no analog functionality:

-          set PCR to all zeros.

-          set the output value of the pin to zero, and set the direction to be an output.

-          Pull the pin to 3.3v through a 10K resistor.

-          This setup has the pin disabled, and we see a 3.3v output.

-          To pull low, simply set the PCR MUX value to 1 to enable the GPIO functionality. (Since you’ve already set the value to 0, the pin gets pulled to zero.)

Best Regards,

Robin

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