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LM3481: controller IC operating values at 105 deg C temperature

Gitika Pandey
Prodigy 30 points
Part Number: LM3481

I am using LM3481 controller IC for SEPIC converter design. The sepic parameters are: Vin: 6.5 -40V, Vout: 18V, Iout: 1A. Currently we have supply at input of LM3481 same as Vin of SEPIC. I want to check the maximum values of junction temperature and IC supply current at high operating temperature (105 deg C) to see if there are any issues at 40V supply input voltage to the IC. The maximum supply current, junction temperature etc.. values given in the datasheet are at Vin=12V and temp 25 deg C. What values do we use at 105 deg C and 40V supply input to the IC?

  • 0
    TI__Guru 65470 points

    Hello Gitika,

    Sorry for the late response.

    Independent of the ambient temperature or input voltage, in your system, the device should not overheat, so the junction temperature shall stay below 150C. The internal dissipation is somewhat higher with higher input voltage, as the driving voltage is around 6V, the internal regulator needs to dissipate more at higher input voltage to stay at 6V. So in general if you compare the operation at room temperature and check how hot the device gets, you need to have some more margin if the ambient temperature is already higher.

    But at the end most important is a good thermal connection to the board and some copper area to dissipate the power away from the IC.