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Thread: PIC overheating a 7805 !
www.piclist.com/techref/power.htm?key=7805
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face BY : Mike Blakey email (remove spam text)



The power used and dissipated by the voltage regulator is NOT calculated that way.
the power dissipated by the device is approx. = (Vin-Vout) * quiescent current and
NOT load current. Check the data sheets!





KILLspamharoldhallikainenRemoveMEspamspamBeGoneJUNO.COM on 09/11/2001 18:44:56
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Subject:        Re: [EE]: PIC overheating a 7805 !

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       24V is a bit high! Calculate out the power dissipation
(24V-5V)*LoadCurrent. Take this (in watts) and multiply by the rating of
your heat sink in degrees C/ watt. This should give temperature rise from
ambient.
       Another thing to watch for is oscillating regulators, which get hot.
Check the output on a scope and make sure you've got DC without a bunch
of RF.
       Finally, consider a switching regulator. The inefficiency of using a
linear regulator to go from 24V down to 5V is pretty impressive.

Harold


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