That's junction to ambient temperature rise. Case temperature will be 8-9
degrees less at this amount of power.
Case temperature of 43 degrees Celsius, for instance, is just 109 degrees
Fahrenheit. That's just a really bad fever. :-) It is not at all unusual
for electronic components to operate in that range.
Still, 7805 has the "built in heatsink" if there's room on the CVS.
John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.comThe Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com > -----Original Message-----
> From: ComputerVoltageSources@yahoogroups.com
> [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of harrybissell
> Sent: Tuesday, March 14, 2006 11:48 PM
> To: ComputerVoltageSources@yahoogroups.com
> Subject: Re: [ComputerVoltageSources] Power Supply Connections
>
> OK lets do the math (check my figures)
>
> 78L05 has "100mA with suitable heatsink" and with short leads
> to a PCB... 160C/W junction to ambient. Max junction temp is 125C
>
> .016A x 10V (voltage drop) = .16W x 160 = 25.6C rise over ambient.
>
> Even with a 25C ambient this is going to run HOT. You will not want
> to touch it...
>
> OK, we can use the 7805 which is MUCH better (and bigger).
>