TPA005D02
2-W STEREO CLASS-D AUDIO POWER AMPLIFIER
SLOS227C – AUGUST 1998 – REVISED MARCH 2000
APPLICATION INFORMATION
crest factor and thermal considerations (continued)
Table 4. TPA005D02 Power Rating, 5-V, 4-Ω, Stereo
PEAK OUTPUT POWER
(W)
POWER DISSIPATION
(W/Channel)
MAXIMUM AMBIENT
TEMPERATURE
AVERAGE OUTPUT POWER
4
4
4
4
4
4
2 W (3 dB)
0.56
0.30
0.23
0.20
0.14
0.09
125°C
136°C
139°C
141°C
143°C
146°C
1000 mW (6 dB)
500 mW (9 dB)
250 mW (12 dB)
120 mW (15 dB)
63 mW (18 dB)
DISSIPATION RATING TABLE
PACKAGE
T
A
≤ 25°C
DERATING FACTOR
T
A
= 70°C
T = 85°C
A
5.6 W
44.8 mW/°C
3.5 W
2.9 W
DCA
The maximum ambient temperature depends on the heatsinking ability of the PCB system. Using the 0 CFM
2
data from the dissipation rating table, the derating factor for the DCA package with 6.9 in of copper area on
a multilayer PCB is 44.8 mW/°C. Converting this to Θ
:
JA
1
Θ
JA
Derating
(19)
1
0.0448
22.3°C W
To calculate maximum ambient temperatures, first consider that the numbers from the dissipation graphs are
per channel so the dissipated heat needs to be doubled for two channel operation. Given Θ , the maximum
JA
allowable junction temperature, and the total internal dissipation, the maximum ambient temperature can be
calculated with the following equation. The maximum recommended junction temperature for the TPA005D02
is 150 °C. The internal dissipation figures are taken from the Efficiency vs Output Power graphs.
T
Max
T Max
Θ
P
(20)
A
J
JA
D
(
)
)
(
)
150 22.3 0.14
2
143°C 15 dB crest factor
(
(
)
150 22.3 0.56
2
125°C 3dB crest factor
NOTE:
Internal dissipation of 0.6 W is estimated for a 2-W system with a 15 dB crest factor per channel.
Table 4 shows that for some applications no airflow is required to keep junction temperatures in the specified
range. The TPA005D02 is designed with thermal protection that turns the device off when the junction
temperature surpasses 150°C to prevent damage to the IC. Table 4 was calculated for maximum listening
volume without distortion. When the output level is reduced the numbers in the table change significantly. Also,
using 8-Ω speakers dramatically increases the thermal performance by increasing amplifier efficiency.
22
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