Micrel, Inc.
Substituting PD for PD(max) and solving for the ambient
operating temperature will give the maximum operating
conditions for the regulator circuit. The junction-to-
ambient thermal resistance for the minimum footprint is
250°C/W.
The maximum power dissipation must not be exceeded
for proper operation.
For example, when operating the MIC5501-MYMT at an
input voltage of 3.6V and 300mA load with a minimum
footprint layout, the maximum ambient operating
temperature TA can be determined as follows:
0.240W = (125°C – TA)/(250°C/W)
TA = 65°C
Therefore, the maximum ambient operating temperature
allowed in a 1mm × 1mm DFN package is 65°C. For a
full discussion of heat sinking and thermal effects on
voltage regulators, refer to the “Regulator Thermalsâ€
section of Micrel’s Designing with Low-Dropout Voltage
Regulators handbook. This information can be found on
Micrel's website at:
http://www.micrel.com/_PDF/other/LDOBk_ds.pdf
MIC5501/2/3/4
April 20, 2015
10
Revision 2.3