LM4752T National Semiconductor, LM4752T Datasheet - Page 13

• Manufacturer Part Number: LM4752T
• Description: Stereo 11W Audio Power Amplifier
• Manufacturer: National Semiconductor

Application Information
TO-263 HEATSINK DESIGN EXAMPLES:
Example 1: (Stereo Single-Ended Output)
Given:
P
Calculating P
Calculating Heatsink Thermal Resistance:
Therefore the recommendation is to use 1.5 x 1.5 square
inch of single-sided copper clad.
Example 2: (Stereo Single-Ended Output)
Given:
P
Calculating P
Calculating Heatsink Thermal Resistance:
Therefore the recommendation is to use 2.0 x 2.0 square
inch of single-sided copper clad.
Example 3: (Bridged Output)
Given:
Calculating P
Calculating Heatsink Thermal Resistance:
Therefore the recommendation is to use 2.0 x 2.0 square
inch of single-sided copper clad.
P
DMAX
DMAX
DMAX
SA
P
SA
SA
P
DMAX
DMAX
<
<
<
from P
from P
= 4[V
120˚C / 3.7W − 2.0˚C/W − 0.2˚C/W = 30.2˚C/W
100˚C / 3.7W − 2.0˚C/W − 0.2˚C/W = 24.8˚C/W
100˚C / 3.7W − 2.0˚C/W − 0.2˚C/W = 24.8˚C/W
= V
= V
SA
SA
SA
T
T
R
V
DMAX
T
T
R
V
DMAX
T
T
R
V
DMAX
CC
D
D
JC
JC
JC
A
J
A
J
A
J
S
<
S
CC
S
L
L
L
CC
<
<
= 150˚C
= 150˚C
= 150˚C
= 30˚C
= 4
= 50˚C
= 4
= 50˚C
= 8
= 12V
vs P
= 12V
vs P
= 12V
2
= 2˚C/W
= 2˚C/W
= 2˚C/W
[(T
2
[(T
[(T
2
/ (2
:
:
:
/ (
/ (
J
J
J
O
O
− T
− T
− T
2
2
P
P
Graph:
2
Graph:
R
R
R
DMAX
DMAX
L
L
A
A
L
A
) = (12V)
)] = 4(12V)
) = (12V)
) / P
) / P
) / P
DMAX
DMAX
DMAX
3.7W
3.7W
2
2
] −
] −
] −
/ (
2
/
/ (2
2
2
JC
JC
JC
(Continued)
(4 )) = 3.65W
(4 )) = 3.65W
−
−
2
−
(8 )) = 3.65W
CS
CS
CS
13
Layout and Ground Returns
Proper PC board layout is essential for good circuit perfor-
mance. When laying out a PC board for an audio power am-
plifer, 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 sepa-
rately 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.
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