TPA032D02

10-W STEREO CLASS-D AUDIO POWER AMPLIFIER

SLOS243A – DECEMBER 1999 – REVISED MARCH 2000

19

POST OFFICE BOX 655303

APPLICATION INFORMATION

crest factor and thermal considerations

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 TPA032D02 data sheet, one can see that when the

TPA032D02 is operating from a 12-V supply into a 4-

Ω speaker that 20-W peaks are available. Converting watts

to dB:

P

P

W

P

ref

+ 10Log 20

1

+ 6dB

(17)

Subtracting the crest factor restriction to obtain the average listening level without distortion yields:

6.0 dB

* 15 dB +* 9dB (15 dB crest factor)

6.0 dB

* 12 dB +* 6dB (12 dB crest factor)

6.0 dB

* 9dB +* 3dB (9 dB crest factor)

6.0 dB

* 6dB +* 0dB (6 dB crest factor)

6.0 dB

* 3dB + 3dB (3 dB crest factor)

6.0 dB

* 18 dB +* 12 dB (15 dB crest factor)

Converting dB back into watts:

P

PdB 10

P

ref

+ 630 mW (15 dB crest factor)

+ 1.25 W (12 dB crest factor)

+ 2.5 W (9 dB crest factor)

+ 5 W (6 dB crest factor)

+ 10 W (3 dB crest factor)

(18)

+ 315 mW (18 dB crest factor)

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 10 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 12-V, 4-

Ω system, the internal dissipation in the

TPA032D02 and maximum ambient temperatures are shown in Table 3.