TPA301
350-mW MONO AUDIO POWER AMPLIFIER
SLOS208C – JANUARY1998 – REVISED MARCH 2000
APPLICATION INFORMATION
5-V versus 3.3-V operation
The TPA301 operates over a supply range of 2.5 V to 5.5 V. This data sheet provides full specifications for 5-V
and 3.3-V operation, as these are considered to be the two most common standard voltages. There are no
special considerations for 3.3-V versus 5-V operation with respect to supply bypassing, gain setting, or stability.
The most important consideration is that of output power. Each amplifier in TPA301 can produce a maximum
voltage swing of V
– 1 V. This means, for 3.3-V operation, clipping starts to occur when V
= 4 V at 5 V. The reduced voltage swing subsequently reduces maximum output power into
= 2.3 V as
DD
O(PP)
opposed to V
O(PP)
an 8-Ω load before distortion becomes significant.
Operation from 3.3-V supplies, as can be shown from the efficiency formula in equation 4, consumes
approximately two-thirds the supply power for a given output-power level than operation from 5-V supplies.
headroom and thermal considerations
Linearpoweramplifiersdissipateasignificantamountofheatinthepackageundernormaloperatingconditions.
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 TPA301 data sheet, one can see that when the TPA301
is operating from a 5-V supply into a 8-Ω speaker 350 mW peaks are available. Converting watts to dB:
P
10LogP
10Log 3500 mW
–4.6 dB
dB
W
Subtracting the headroom restriction to obtain the average listening level without distortion yields:
(
19.6 dB 15 dB headroom
)
)
–4.6 dB 15 dB
–4.6 dB 12 dB
–4.6 dB 9 dB
–4.6 dB 6 dB
–4.6 dB 3 dB
(
16.6 dB 12 dB headroom
(
)
)
13.6 dB 9 dB headroom
(
10.6 dB 6 dB headroom
(
)
7.6 dB 3 dB headroom
Converting dB back into watts:
PdB 10
P
10
W
11 mW (15 dB headroom)
22 mW (12 dB headroom)
44 mW (9 dB headroom)
88 mW (6 dB headroom)
175 mW (3 dB headroom)
18
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265