TPA0103PWPRG4 Datasheet, PDF (35/45 Pages) Texas Instruments – 1.75-W 3-CHANNEL STEREO AUDIO POWER AMPLIFIER

TPA0103
1.75-W 3-CHANNEL STEREO AUDIO POWER AMPLIFIER
SLOS167A – JULY 1997 – REVISED MARCH 2000
APPLICATION INFORMATION
headroom and thermal considerations
Linear 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 headroom to pass the loudest portions without distortion
as compared with the average power output. From the TPA0103 data sheet, one can see that when the
TPA0103 is operating from a 5-V supply into a 4-Ω speaker that 2 W RMS levels are available. Converting watts
to dB:
+ ǒ Ǔ P_dB
10 Log
P_W
P_ref
+ ^{ǒ Ǔ} 10Log
2
1
+ 3 dB
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
* + * 3 dB 15 dB
12 dB (15 dB headroom)
Converting dB back into watts:
+ ^ń P_W
10^{PdB 10} P_ref
+ * + P_W
12 dB 63 mW (15 dB headroom)
This is valuable information to consider when attempting to estimate the heat dissipation requirements for the
amplifier system. Comparing the absolute worst case, which is 1.5 W of continuous power output with 0 dB of
headroom, 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, 4-Ω system, the internal dissipation in the TPA0103
and maximum ambient temperatures is shown in Table 4.
Table 4. TPA0103 Power Rating, 5-V, 4-Ω, Three Channel
CONFIGURATION
HEADROOM†
POWER DISSIPATION
2 × L/R + CENTER = TOTAL
TA (MAX)‡
35°C/W
25°C/W
Center only, PO = 2 W max
0 dB
15 dB
0
1.25 W 1.25 W
81°C
0
0.6 W 0.6 W
104°C
93°C
110°C
L/R only, PO = 500 mW max
0 dB
15 dB
0.6 W
0
1.2 W
0.2 W
0
0.4 W
83°C
111°C
95°C
115°C
Center, PO = 2 W max
0 dB
0.6 W 1.25 W 2.45 W
39°C
63°C
and
L/R , PO = 500 mW max
15 dB
0.2 W 0.6 W
1W
90°C
100°C
† _{The 2 W max at 0 dB is a maximum level tone that is very loud. 15 dB is a typical headroom requirement for music.}
‡ _{This parameter is based on a maximum junction temperature (TJ) of 125°C.}
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