MIC5353 Datasheet, PDF (8/12 Pages) Micrel Semiconductor – 500mA LDO in 1.6mm × 1.6mm Package

Micrel, Inc.
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 = (3.3V – 2.8V) × 500mA
P_D = 0.25W
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:
⎛ ^TJ(MAX) ^{- T}A
⎝ ^{PD(MAX) =}
JA
T_J(max) = 125°C, the maximum junction temperature of
the die θ_JA thermal resistance = 92.4°C/W.
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
92.4°C/W.
MIC5353
The maximum power dissipation must not be exceeded
for proper operation.
For example, when operating the MIC5353-2.8YMT at
an input voltage of 3.3V and 500mA load with a
minimum footprint layout, the maximum ambient
operating temperature T_A can be determined as follows:
0.25W = (125°C – T_A)/(92.4°C/W)
T_A=101°C
Therefore, a 2.8V application with 500mA of output
current can accept an ambient operating temperature of
101°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 2010
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M9999-052510