7805 voltage regulator

[mojorizing]

I'm looking at a circuit used in a treadmill. There's a 7805 with the center (ground lead) that is clipped off and not connected. Why is this 7805 used this way? I recall long ago that this is configured as a current limiter, but I could be wrong.....Could someone get me up to speed on this?

Thanks, Kevin

[dyarker]

On 78xx regulators the heat sink tab is also "ground" lead. In the treadmill, they could be making reference connection through the tab. Clipping off the lead leaves room on the PCB for larger traces.

Cheers,

[dacflyer]

ya thats right...

also note they make a plastic case type also..but the tab is non-metallic
so the middle legg would need to be used in that case.

look on the underside of the board, you should see a contact connected to the tab of that regulator..

[mojorizing]

Bingo! The tab is solder to the ground plane...thanks for the responses.

later, Kevin