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Original question:

LM137: lm137 power dissipation

LM137: Current limit of TO3 package

Francesco Buonomo2
Prodigy 210 points
Part Number: LM137

Which is the current limit of TO3 package without dissipation if I have input voltage of -4.25V and output voltage of -1.25V.

The Vin-Vout<15V so the current limit in the datasheet is between 0.5A and 1.8A.

With thermal dissipation of 140°C/W and with minimum current limit of 0.5A the deltaT between junction and ambient that I have is 140°C/W*(4.25V-1.25V)*0.5A=210°C

Thank you for your support

Francesco B.

  • 0
    TI__Mastermind 28455 points

    Hey Francesco,

    It is possible that without a heatsink the device goes into thermal shutdown before it hits the current limit.

    Adding a heatsink will greatly decrease the thermal dissipation and allow for the device to more predictably hit the current limit rather than the thermal shutdown.

    This should not change the current limit of the device itself at a given Vin-Vout and temperature.

    All information about the profile of the current limit is shown in Figure 2.

    Thanks,

    Daniel