When the open-drain output enable of a pin is changed from 1 to 0, what is the difference between this output state and push-pull output?

一沙一世

When the open-drain output enable of a pin is changed from 1 to 0, what is the difference between this output state and push-pull output? [Copy link]

邀请：@maychang   @chunyang   @damiaa   @dcexpert   参与回复

When the open-drain output enable of a pin is changed from 1 to 0, what is the difference between this output state and push-pull output?

maychang

"When the open-drain output enable of a pin is changed from 1 to 0, what is the difference between this output state and push-pull output?"

In this state, there is not much difference, both lower tubes are turned on. The difference is that the upper tube of the push-pull output is turned off and there is no current, while the pull-up resistor of the open-drain output still has current, and this current is conducted away by the lower tube.

一沙一世

maychang posted on 2022-5-17 19:17 "When the open-drain output enable of a pin is changed from 1 to 0, what is the difference between this output state and push-pull output?" As far as this state is concerned, there is no more...

Thank you very much. However, I don't understand what you mean. As shown in the figure below, there is no connection between the pull-up resistor and the lower NMOS tube. You said that [there is still current in the pull-up resistor of the open-drain output, and this current is conducted away by the lower tube] I don't understand where the current in the pull-up resistor flows to the lower tube? Thank you again.

maychang

Yishayishi published on 2022-5-18 09:12 Thank you very much. However, I don't understand what you mean. As shown in the figure below, there is no connection between the pull-up resistor and the lower NMOS tube. What you said [and...

I don't understand where the current in the pull-up resistor flows to the lower tube?

chunyang

The open-drain output and push-pull output are the same when outputting logic 0. The difference is that when outputting logic 1, the open-drain output requires an external pull-up to achieve a logic 1 level, while the push-pull output is strongly pulled up to logic 1 by the internal MOS tube.

davidzhu210

When the open drain output is 0, it is no different from the push-pull output, and the output is low level, close to ground.