What should I do with unused outputs?

[Braeden Hamson]

First off, damn this new website looks nice!

I really feel like I should know this answer but just to be safe. I'm going to use a 74HC163 without any other counters.

http://www.ti.com/lit/ds/symlink/sn74hc163.pdf ←Datasheet

Therefore I don't need the "carry out" pin. I know that you should always ground unused inputs but should I be grounding outputs?
I know it wont short out if I ground this pin because of the internal resistors within the gates of the CO.

Thanks!

 

[Audioguru]

If you ground an output then it is shorted to ground. Then there will be damage when it tries to go high. The outputs use powerful Mosfets without any resistors to limit the current.
Leave the unused output with nothing connected to it and it will be fine.

 

[BobK]

Do you understand why unused inputs should be grounded? Does that reason apply to outputs?

Bob

 

[73's de Edd]

SEND THEM TO ME !
I can dern sure use them . . . . they will be well received . . . and therefore, not be wasted.

 

[Audioguru]

I don't have many unused outputs but instead I have a lot of amplifier power that is rarely used. I hate audio distortion and never play acid rock so I keep my amplifiers away from full power clipping. It would be good if I could save then later reuse the unused extra power.

Remember when AA battery cells had a label on the side that burned to show the amount of charge left in them? If the test was done a more than a few times then it killed the battery almost like when people continuously short a battery to keep the electrons from leaking out.

 

[BobK]

While we are on unused things...

The X86 processors in our PC’s have hundreds of instructions, most of which are never used by the typical user. It would be nice if we could sell these on Ebay to people who need more instructions.

Bob

 

[Harald Kapp]

should I be grounding outputs?

What about your wall outlets when not used. Do you 'ground' them?

The short and sweet answer (to bothe questions) is: NO.

 

[Audioguru]

The absolute maximum allowed output current of your 74HC163 is 25mA. But it has enough power to conduct 68mA into a shorted output which will destroy it. If you connect an output to ground (which is a logic low) but an input causes its output to try to go to a logic high then it will be destroyed.