Open Collector Outputs

• To tie devices together and share outputs a special output called an “Open Collector Output” is used.

  • Has two states: 0 (ground) or float (non-determined)
  • Basically: This output pin has no capability of supplying power to the pin and therefore cannot try to hold the line high while somebody else drives it low.
  • Cannot be used to signal a 1 without external glue logic such as a pull-up resistor.