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LMR33630CDDAEVM: Excessive heat dissipation

Part Number: LMR33630CDDAEVM


We have made a prototyping circuit around the LMR33630C SOIC package and have some major heating issues.

We are stepping down a 12v supply to 5v, and driving a resistive load of 6 Ohms which draws about 1 Ampere of current. The schematic is as follows:

Even while only drawing 1A of current, the IC is heating up excessively, post which it enters "hiccup mode" to limit current.

Even adding a makeshift heatsink to the thermal pad did not help much in dissipating the heat:



  1. We have used two 1.2uH Inductors of unknown saturation current rating (sourced locally) in series, to get the needed value for L1(which was calculated by WEBENCH) .
  2. Could Inductor core saturation be a possible cause of excessive heating at relatively nominal (1A) load?
  3. Is the 6 ohm resistive load acting as a sustained short circuit (thus the hiccup mode) ?
  4. Should buck converter switching losses heat up the IC so much?

Any help would be appreciated!