Micrel, Inc.

MIC5501/2/3/4

April 20, 2015

10

Revision 2.3

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 Thermals”

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