True Open Drain and High Sink Capability in Microcontroller GPIO pins meaning?

Submitted by Ashutosh on Tue, 06/16/2020 - 09:13

I am doing some bare metal programming for a 8-bit microcontorller. The datasheet mentions that few of the GPIO pins have "True Open Drain" while the others have "High Sink Capability". What does it actually mean? I know GPIO pins can be of Open-Drain or Push pull type and I know whats the meaning of that. But what is the difference between just "Open-Drain" and "True Open Drain"? Also what is High Sink Capability?

The mcu that states open drain is not actually open drain, it has internal circuitry that mimic the open drain charecteristics but for true open drain they are connected to the FET drain. May be I am wrong, but you could also check datasheet of the respective datasheet of the controller.

High sink capabilities stands for high current sink. so it will sink high current more than 60mA (Always check datasheet and the I/O section before operations) of current through the I/O port.

  Joined February 12, 2018      696
Monday at 02:11 PM

For the true open drain pins, the voltage seen on it can go above Nominal voltage level as per datasheet.Open drain outputs require a pull-up resistor for the output to be able to properly “output high”. The pull-up resistor is connected between the output pin and the output voltage.

  Joined August 22, 2019      125
Thursday at 12:29 PM