MIC5313 Datasheet, PDF (9/12 Pages) Micrel Semiconductor – Low Voltage Dual 300mA LDO

Micrel, Inc.
To determine the maximum ambient operating
temperature of the package, use the junction-to-ambient
thermal resistance of the device and the following basic
equation:
P_D(MAX)
=
⎜⎛ ^{TJ(MAX) − TA}
⎜⎝
θ _JA
⎟⎞
⎟⎠
T_J(max) = 125°C, the maximum junction temperature of
the die. The junction-to-ambient thermal resistance for
the minimum footprint, is θ_JA = 80°C/W.
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 maximum power dissipation must not be exceeded
for proper operation.
MIC5313
For example, when operating the MIC5313-FCYMT at
an input voltage of 1.8V and 300mA, loads at each
output with a minimum footprint layout, the maximum
ambient operating temperature T_A can be determined as
follows:
0.33W = (125°C – T_A)/(80°C/W)
T_A = 98.6°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
July 2008
9
M9999-070208-A