MIC5321_08 Datasheet, PDF (10/12 Pages) Micrel Semiconductor – Dual, High Performance 150mA μCap ULDO™

Micrel, Inc.
Substituting P_D for P_D(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 100°C/W.
The maximum power dissipation must not be
exceeded for proper operation.
For example, when operating the MIC5321-MFYMT at
an input voltage of 3.3V and 150mA loads at each
output with a minimum footprint layout, the maximum
ambient operating temperature T_A can be determined
as follows:
MIC5321
0.345W = (125°C – T_A)/(100°C/W)
T_A=90.5°C
Therefore, a 2.8V/1.5V application with 150mA at
each output current can accept an ambient operating
temperature of 90.5°C in a 1.6mm x 1.6mm Thin
MLF^® package. 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
May 2008
10
M9999-051508-E