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LM2576 overheat when i put a charge of 500mA

Yannick Yapo
Prodigy 70 points
Part Number: LM2576

Hello,

I have bought a LM2576 for my project because I need 5V to supply my STM32 and an external peripheral device from a 36V Battery.  Currently; i'm testing the lm2576 on a breadboard with a 31.6V Lab Alimentation.

When i'm testing the circuit without charge, all is fine, however when i put a 10 ohm resistor which means a current of 500mA, the LM2576 starts to overheat and i can smell it burning inside.

This is the circuit from WEBECH for :

I took :

Cin : 330uF ,50V , 580 mA

Cout : 680uF ,10V , 660 mA

D1 : 1N5822+

L1 : 150uH Irms 3.4A

Normally, the LM2576 can supports 3A. So I'm asking why it overtheats for 500mA and what will happen to the voltage regulator if the current is above 3A ? or during short circuit ? Do I need to use a fuse or LM2576 has a protection ?

This is my breadboard :

  • 0
    TI__Mastermind 25590 points

    Yannick,

    A breadboard has lots of parasitic inductances which may be affecting performance. See figure 34 in the datasheet for the example layout. Try rearranging components and shortening some wires to minimize the loop area in the following loops:

    • CIN+ to the VIN pin to the GND pin to CIN- 
    • GND pin to diode anode to diode cathode, to the OUTPUT pin

    Also try soldering a small (0603 ceramic) 470nF or greater capacitor to the VIN pin and GND pin. Solder this onto the pins to minimize the loop. Place the capacitor very close to the pins if creating a custom circuit board.

    -Sam

  • 0 in reply to Samuel Jaffe
    TI__Mastermind 25590 points

    Yannick,

    One more very important note that I overlooked. You will probably need a heatsink. Typically the IC is soldered to a PCB with copper to spread the heat which acts as the heatsink. If your circuit will remain on the breadboard, you will need an additional heatsink.

    You should also add an electrical connection from the heatsink metal tab to GND.

    -Sam