MIC5314 Datasheet, PDF (11/14 Pages) Micrel Semiconductor – Low Voltage Dual 300mA LDO with Power on Reset

Micrel, Inc.
be determined using the equation:
P_D = (V_IN – V_OUT1) I_OUT1 + (V_IN – V_OUT2) I _OUT2 + V_BIAS I_GND
Because this device is CMOS and the ground current is
typically <100µA over the load range, the power
dissipation contributed by the ground current is < 1%
and can be ignored for this calculation.
P_D = (1.8V – 1.5V) × 300mA + (1.8V – 1.0V) × 300mA
P_D = 0.33W
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 = 70°C/W.
MIC5314
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.
For example, when operating the MIC5314-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)/(70°C/W)
T_A = 101.9°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
11
M9999-070208-A