Request For Thermal Resistance

Nitheesh shenoy 

The datasheet includes the thermal resistance from the die surface (Junction) to the top of the case (Rjc) value - 1.9C/W, but does not include the junction to bottom of case (Rjb) value.  I will look to see if I can find the exact details of the resistance, but the active silicon inside the LMZ12003TZ-ADJ is thermally attached to the 5.3 x 8.5mm exposed thermal pad on the bottom side of the package.  This should provide the device with a thermal resistance to the bottom of package of less than 2C/W.  With this low thermal resistance, the total thermal resistance from junction to ambient will be dominates by external factors, such as the thermal spreading in the PCB and thermal resistance from the PCB to the ambient air.

Until we are able to provide you with more detailed numbers, you should be able to start your modeling with a thermal resistance to the bottom of the case of 1C/W.

Thank you..

I will start my analysis with 1 C/ W..