Open Drain i/o or Open Collector i/o

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Hi all

I am new in Hardware design .
I have seen Open Drain pin in a controller ,so what does it mean . Can i use it as input or output . how to use it .Some of documents say it should be pull up with a Vcc ,why should be so , if i connect it with GND .


Thanks in Advnace
 

It means It can give only gnd or high impedance state as the output....

so if you pulled it up then the high impedance state will be high....

It is employed in some controllers because to ensure the compatibility between different Vcc logics......
 

Thanks for the reply.

how it high impedance or low impandce being used here .How do Pull up work here .pls elobrate your answer as i am confuse after searching many web sources .

Thanks
 

This is called open collector configuration,

If the transistor is switched ON the output will be low...
and if it is turned OFF there is no connection in the output pin that is considered as the high impedance state ((if you connected a pull up it will be now high or vcc)there is no term called low impedance state)...
 

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