MIC5357 Datasheet, PDF (8/11 Pages) Micrel Semiconductor – High Performance, Low Noise Dual 500mA ULDO™

Micrel, Inc.
Thermal Resistance
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
64.4°C/W.
The maximum power dissipation must not be exceeded
for proper operation.
For example, when operating the MIC5357 at an input
voltage of 3.6V and 500mA on V_OUT1 and 500mA on
V_OUT2, the maximum ambient operating temperature T_A
can be determined as follows:
0.55W = (125°C – T_A)/(64.4°C/W)
T_A = 89.6°C
MIC5357
Therefore, a 3.3V/2.8V application with 500mA and
500mA output currents can accept an ambient operating
temperature of 89.6°C in a small 8 Pin ePAD MSOP
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
January 2011
8
M9999-011311