Datasheet

TPA0202
2-W STEREO AUDIO POWER AMPLIFIER
SLOS205B – FEBRUARY 1998 – REVISED DECEMBER 2000
38
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
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 TPA0202 data sheet, one can see that when the
TPA0202 is operating from a 5-V supply into a 3-Ω speaker that 2 W peaks are available. Converting watts to
dB:
P
dB
10Log
P
W
P
ref
10Log
2
1
3.0 dB
(17)
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
3.0 dB 15 dB 12 dB
(
15 dB headroom
)
3.0 dB 12 dB 9dB
(
12 dB headroom
)
3.0 dB 9dB 6dB
(
9 dB headroom
)
3.0 dB 6dB 3dB
(
6 dB headroom
)
3.0 dB 3dB 0dB
(
3 dB headroom
)
Converting dB back into watts:
P
W
10
PdB 10
P
ref
63 mW (15 dB headroom)
120 mW (12 dB headroom)
250 mW (9 dB headroom)
500 mW (6 dB headroom)
1000 mW (3 dB headroom)
(18)
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 2 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, 3-Ω system, the internal dissipation in the TPA0202
and maximum ambient temperatures is shown in Table 4.