please dont rip this site

Open Collector


Q is the value in the internal register corresponding to the output pin. Usual CMOS output: When Q is high, P is off and N is on. When Q is low, P is on and N is off.
(TTL is the same except P is PNP and N is NPN)

Vcc-------+
          |
      ---[ P channel FET
     |    |
Q ---|    +----------Out
     |    |
      ---[ N channel FET
          |
Vss-------+
Open drain output: When Q is high, N is on, output sinks current. When Q is low, N is off, output is high-impedance.
Vcc-------+ (a pullup resistor between Vcc and Out gives you a logic 1 when
N is off)
          +--------- Out
          |
     Q ---[ N channel fet
          |
Vss-------+

This configuration is often used in what is called 'wired OR'. Any number of open-drain devices can sit on the same bus, with an external pull-up resistor. The un-asserted state is high (negative logic). Any one of the devices on the bus can pull the signal low to its asserted state, hence creating an OR function on the bus.

The open-collector is often used on interrupt lines. A number of devices sit on the one interrupt signal, and any one of the devices can assert the signal by driving it low. You can add and remove devices from the bus as necessary. This wouldn't be possible with normal logic outputs, because one device would be driving the bus high while another would be driving it low. But an open drain can't drive a signal high, hence the need for an external pull-up. It can only pull a signal low.

See also:


file: /Techref/logic/opencollector.htm, 1KB, , updated: 2005/7/27 09:34, local time: 2014/9/16 04:27, owner: JMN-EFP-786,
TOP NEW HELP FIND: 
54.166.8.138:LOG IN

 ©2014 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE! / 

<A HREF="http://www.piclist.com/techref/logic/opencollector.htm"> Open Collector</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

  PICList 2014 contributors:
o List host: MIT, Site host massmind.org, Top posters @20140916 RussellMc, Richard R. Pope, IVP, John Gardner, alan.b.pearce, David C Brown, James Cameron, Bob Blick, Josh Koffman, Isaac Marino Bavaresco,
* Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.
 

Welcome to www.piclist.com!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .