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LM317: LM317 output current capacity and efficiency under 85℃ condition

Wayne Wang20
Expert 4360 points
Part Number: LM317

Hi team,

My customer wants to use LM317 in a equipment on the high speed train. So they care about the performance under high temperature condition very much. So could you please help on below question:

1. what is the maximum output current under 85℃? Is it still 1.5A as datasheet states?

2. Do we have a curve between the maximum output current and temperature?

Thanks.

Best regards

Wayne

  • 0
    TI__Mastermind 38045 points

    Hi Wayne,

    The 1.5A specification in the datasheet refers to the current limit circuitry and does not represent the maximum current for a given temperature. The reason for this is that the maximum output current at a given temperature is also dependent on the input and output voltage. To answer the questions I would need more information regarding the application.

    1) What package does the customer want to use? Since they are interested in a high-temperature application, the KCS package would be recommended with a heat sink since it has the best thermal performance according to the datasheet.

    2) What is the input and output voltage? 

    3) What are the expected loading conditions?

    We do not have a maximum output current vs. temperature curve, but we can estimate what the maximum output current will be to avoid thermal shutdown with the information in these questions. 

    Regards,

    Nick