Datasheet

LM4755
www.ti.com SNAS010E –FEBRUARY 1999–REVISED APRIL 2013
θ
SA
< 100°C/3.7W − 2.0°C/W − 0.2°C/W = 24.8°C/W (11)
Therefore the recommendation is to use 2.0 × 2.0 square inch of single-sided copper clad.
Example 3:(Bridged Output)
Given: T
A
=50°C
T
J
=150°C
R
L
=8Ω
V
S
=12V
θ
JC
=2°C/W
Calculating P
DMAX
:
P
DMAX
= 4[V
CC
2
/(2π
2
R
L
)] = 4(12V)
2
/(2π
2
(8Ω)) = 3.65W (12)
Calculating Heatsink Thermal Resistance:
θ
SA
< [(T
J
− T
A
) / P
DMAX
] − θ
JC
− θ
CS
(13)
θ
SA
< 100°C / 3.7W − 2.0°C/W − 0.2°C/W = 24.8°C/W (14)
Therefore the recommendation is to use 2.0 × 2.0 square inch of single-sided copper clad.
LAYOUT AND GROUND RETURNS
Proper PC board layout is essential for good circuit performance. When laying out a PC board for an audio
power amplifier, particular attention must be paid to the routing of the output signal ground returns relative to the
input signal and bias capacitor grounds. To prevent any ground loops, the ground returns for the output signals
should be routed separately and brought together at the supply ground. The input signal grounds and the bias
capacitor ground line should also be routed separately. The 0.1 µF high frequency supply bypass capacitor
should be placed as close as possible to the IC.
Copyright © 1999–2013, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Links: LM4755