Linear regulator with 250mA output

[samppa]

Hi, I thought about upping this old thread.

Did you ever finish testing?

I have been in a same kind of situation myself. I have a SOIC8 cased regulator and measured the surface temperature with a ir meter at 55 celcius. Do you think this is too hot? The system is working, but how much am I compromising the reliability? The calculated power dissipation should be about 0.35 W.

 

[karesz]

Hi,
Check pls the datasheet of your regulator for Thermal resistance of junction-case/ambient...
Its maybe some at 10--20celsius/Watt & 30--60 or even at 100Celsius/Watt...
Otherwise what an IR meter measures is not an absolute value_has relative big uncertanity because the needed emissions correction, but is a good orientation.
Also a temperature with ca. 55 celsius with an environment of maybe 25 celsius_must means that your regulator will not overheated(if the measured 55 celsius was taken at full load)...
K.

 

[samppa]

Thanks for a quick reply!

My regulator's datasheet only says that the junction-to-air thermal resistance is 160 C/W. Other thermal resistances are not told. But it's a normal SOIC8 case, and the calculated power dissipation is about 0.35 W.

The 55 Celcius reading was taken at full load, and I know that the regulator is not acutely overheating as everything works OK. But I was wondering if I am compromising the regulator's long term reliability if I continue running this system for 24/7 Or should I add a heat sink (which would be very hard at this point)?