Burned up my first chip!

[Orin Eman]

<Snip>

> I think I shorted two of the leads coming out of the chip with the
> voltmeter probes.  1) Did that do it? 2) Inputing 12 volts didn't do it,
> did it?  3) Did having no load do it?  4) Does it need a heat sink which
> is why the back side was nice and shiney?

You shouldn't have any trouble with 12V.  You might want a small heatsink
if you want to take 1A out of it at 5V - it will be dissipating 7W.

If you are planning to run this off the car's electrical system,
you will need a little protection before the 7805...

I use 12V -> resistor -> 1N4004 -> 27V TVS to ground, big cap to ground,
7805 input.

This protects the 7805 against various transients and voltage
reversals on the 12 V supply.  The big cap powers the 7805
during voltage dropouts on the 12V supply - use 100 to 300 uF, 35V.
The resistor is mainly to help soak up transients rather than
letting the TVS do all the job.  I use 22 ohm 1/2W for a circuit
requiring 100mA or so.  2.2 ohm 5W would be good for a circuit
requiring 1A, but use a _big_ (1.5KE at least) TVS.

Orin.