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LM2576: Datasheet problem

Yannick Yapo
Prodigy 70 points
Part Number: LM2576

Hello !

I have a LM2576 (TO-220) that heats a lot. However, according to the datasheet's calculations it should not have heat so much because the load demand 300mA. So I decided to put a heat sink , I noticed that rthjc>rthja so if i put a heat sink , it will heat much more according to this data. Is it a mistake from the datasheet or I I did not understand how to calcul the thermal resistance.

Design :

Datasheet :

  • +1
    TI__Mastermind 27030 points

    HI

    Theta JA is based on JEDEC standard, from the data, the heat dissipation have two way , one is from junction to bttom and another is from junction to top case.  so the total theta JA can be smaller than Rtheta JC top. more like two thermal resistance paralleling. 

    Thanks