Datasheet

www.ti.com
TPA721
SLOS231E – NOVEMBER 1998 – REVISED JUNE 2004
Converting dB back into watts:
P
W
= 10
PdB/10
= 22 mW (15-dB headroom)
= 44 mW (12-dB headroom)
= 88 mW (9-dB headroom)
= 175 mW (6-dB headroom)
= 350 mW (3-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 700 mW 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, 8-Ω system, the internal dissipation in the TPA721 and
maximum ambient temperatures is shown in Table 2 .
Table 2. TPA721 Power Rating, 5-V, 8-Ω BTL
D PACKAGE DGN PACKAGE
(SOIC) (MSOP)
PEAK OUTPUT AVERAGE POWER
POWER OUTPUT DISSIPATION
MAXIMUM AMBIENT MAXIMUM AMBIENT
(mW) POWER (mW)
TEMPERATURE TEMPERATURE
(0° CFM) (0° CFM)
700 700 mW 675 34°C 110°C
700 350 mW (3 dB) 595 47°C 115°C
700 176 mW (6 dB) 475 68°C 122°C
700 88 mW (9 dB) 350 89°C 125°C
700 44 mW (12 dB) 225 111°C 125°C
Table 2 shows that the TPA721 can be used to its full 700-mW rating without any heat sinking in still air up to
110°C and 34°C for the DGN package (MSOP) and D package (SOIC), respectively.
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