MIC2873 Datasheet, PDF (19/24 Pages) Micrel Semiconductor – 1.2A High-Brightness Flash LED Driver with Single-Wire Serial Interface

Micrel, Inc.
Where the real board area differs from 1 inch square, θ_CA
(the PCB thermal resistance) values for various PCB
copper areas can be taken from Figure 7. Figure 7 is taken
from Designing with Low Dropout Voltage Regulators
available from the Micrel website (“LDO Application
Hints”).
Figure 7. Graph to Determine PC Board Area for a Given
PCB Thermal Resistance
Figure 7 shows the total area of a round or square pad,
centered on the device. The solid trace represents the
area of a square, single sided, in horizontal orientation,
solder masked, copper PC board trace heat sink,
measured in square millimeters. No airflow is assumed.
The dashed line shows PC boards trace heat sink covered
in black oil-based paint and with 1.3m/s (250 feet per
minute) airflow. This approaches a “best case” pad heat
sink. Conservative design dictates using the solid trace
data, which indicates that a maximum pad size of 5000
mm² is needed. This is a pad 71mm × 71mm (2.8 inches
per side).
MIC2873
July 17, 2014
19
Revision 1.0