bob_s Posted October 23, 2004 Report Share Posted October 23, 2004 I've been trying to power an LCD module using a UA78M05CKTPR regulator (power-flex package) but the regulator gets very hot. I measured it with a temperature probe and its more than 155F which is too high. The max operating temp is 150F and the recommended operating temp is 125F. The LCD LED backlight requires 5v at 210ma and I also 5 other LED's (10ma each). I am supplying the regulator with a regulated 12v. I thought at 250ma a heat sink would not be required as it only needs to dissipate 3 watts of power, 12v x 250ma = 3W (although I have soldered it on a 1 inch square on an FR4 0.062" copper PCB) . I had this same circuit working just fine when I powered it with an unregulated 8v at 2 watts of power but I needed the 12v for another addition to the circuit. I have two other regulators off of the same 12v. One at 5v (50ma) and the other at 3.3v (100ma) and neither of them even get warm. So why would the extra 4v cause such a problem? I've attached the datasheet for the regulator.Thanks for any help.BobUA78M00_Series.pdf Quote Link to comment Share on other sites More sharing options...
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