參數(shù)資料
型號(hào): TPA0142PWP
廠商: TEXAS INSTRUMENTS INC
元件分類: 音頻控制
英文描述: 2 CHANNEL(S), VOLUME CONTROL CIRCUIT, PDSO24
封裝: GREEN, PLASTIC, HTSSOP-24
文件頁數(shù): 17/35頁
文件大小: 804K
代理商: TPA0142PWP
www.ti.com
CREST FACTOR AND THERMAL CONSIDERATIONS
P
dB + 10 Log
P
W
P
ref
+ 10 Log
4 W
1 W
+ 6 dB
(9)
TPA0142
SLOS248E – JUNE 1999 – REVISED SEPTEMBER 2004
Class-AB power amplifiers dissipate a significant amount of heat in the package under normal operating
conditions. A typical music CD requires 12 dB to 15 dB of dynamic range, or headroom, above the average
power output, to pass the loudest portions of the signal without distortion. In other words, music typically has a
crest factor between 12 dB and 15 dB. When determining the optimal ambient operating temperature, the internal
dissipated power at the average output power level must be used. From the data sheet, one can see that when
the device is operating from a 5-V supply into a 3-
speaker that 4-W peaks are available. Use Equation 9 to
convert watts to dB.
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
6 dB - 15 dB = -9 dB (15-dB crest factor)
6 dB - 12 dB = -6 dB (12-dB crest factor)
6 dB - 9 dB = -3 dB (9-dB crest factor)
6 dB - 6 dB = 0 dB (6-dB crest factor)
6 dB - 3 dB = 3 dB (3-dB crest factor)
Converting dB back into watts:
PW = 10
PdB/10
× P
ref
= 63 mW (18-dB crest factor)
= 125 mW (15-dB crest factor)
= 250 mW (9-dB crest factor)
= 500 mW (6-dB crest factor)
= 1000 mW (3-dB crest factor)
= 2000 mW (0-dB crest factor)
This is valuable information to consider when estimating the heat-dissipation requirements for the amplifier
system. Comparing the worst case, 2 W of continuous power output with a 3-dB crest factor, against 12-dB and
15-dB applications, drastically affects maximum ambient temperature ratings for the system. Using the power
dissipation curves for a 5-V, 3-
system, the internal dissipation and maximum ambient temperatures are shown
in the table below.
Table 4. TPA0142 Power Rating, 5-V, 3-
Stereo
PEAK OUTPUT POWER
POWER DISSIPATION
MAXIMUM AMBIENT
AVERAGE OUTPUT POWER
(W)
(W/Channel)
TEMPERATURE (1)
4
2 W (3 dB)
1.7
-3
°C
4
1000 mW (6 dB)
1.6
6
°C
4
500 mW (9 dB)
1.3
24
°C
4
250 mW (12 dB)
1.0
51
°C
4
125 mW (15 dB)
0.9
78
°C
4
63 mW (18 dB)
0.6
85
°C
(1)
Package limited to 85
°C ambient
24
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