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LM317A: Output Voltage drop when applying the load

Jack Shen2
Expert 4015 points
Part Number: LM317A

We would like to use LM317A for the application which has 12V Vin and 3.3V Vout for 1.0A Iout. We tried LM317A with the EVM (LM317A-337N-EVM), however, we found out that when we started applying the load from 0.1A to 1.0A, we saw that the output voltage (3.3V) begin to drop and could not stabilized the output voltage in 3.3V. 

May I have your support to provide the guidance to know what other things need to look for? thanks.  

  • 0
    TI__Expert 3675 points

    Hello Jack,

    Dropping 12V down to 3.3V at 1A is 8.7W of dissipation across the LDO. I suspect that the die is heating up to a point where thermal shutdown is kicking in. 

    Perhaps a buck converter can be used to lower the voltage so there is not as much dissipation across the LDO.

    ~ Aaron