Hi!
Does anyone have an easy solotion on how to overvoltage protect some digital in- and outputs? Im going to have 5V digital inputs and outputs from an uControler. These signals shall withstand that someone connects +12V to them. On the inputs i can use a series resistor with a zenerdiode. But how about the outputs..? Any suggestions on how to solve that in an easy way? Some kind of buffer solution?
The usual solution for buffering and protecting the outputs is an open- collector or open drain buffer.
The classical open collector inverting buffer is the SN7406, which can take up to 30V across the collector
It is a very old device - I first used it back in 1971 - and while Farnell still stocks it, there are many similar devices available.
-- Bill Sloman, Nijmegen
It is called an open collector non-inverting buffer - you supply a pull up resistor to the +12 V source for an output or put your load between +12 V and the OC if it can be driven with the current the buffer is rated at.
Some controllers, and many digital logic IC's do offer OC outputs for that reason.
Here's another immortal chip from the 70s, one of my all-time favorites -
Best regards, Ralph in NH
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