TPA0222 Datasheet, PDF (29/33 Pages) Texas Instruments – STEREO 2-W AUDIO POWER AMPLIFIER WITH FOUR SELECTABLE GAIN SETTINGS AND MUX CONTROL

TPA0222
STEREO 2-W AUDIO POWER AMPLIFIER
WITH FOUR SELECTABLE GAIN SETTINGS AND MUX CONTROL
SLOS285 – NOVEMBER 1999
APPLICATION INFORMATION
crest factor and thermal considerations (continued)
Table 5. TPA0222 Power Rating, 5-V, 8-Ω, Stereo
PEAK OUTPUT POWER
2.5 W
2.5 W
2.5 W
2.5 W
AVERAGE OUTPUT POWER
1250 mW (3 dB crest factor)
1000 mW (4 dB crest factor)
500 mW (7 dB crest factor)
250 mW (10 dB crest factor)
POWER DISSIPATION
(W/Channel)
0.55
0.62
0.59
0.53
MAXIMUM AMBIENT
TEMPERATURE
100°C
94°C
97°C
102°C
The maximum dissipated power, P_Dmax, is reached at a much lower output power level for an 8-Ω load than for
a 3-Ω load. As a result, this simple formula for calculating P_Dmax may be used for an 8-Ω application:
+ P_Dmax
2V^2DD
p²R_L
(11)
However, in the case of a 3-Ω load, the P_Dmax occurs at a point well above the normal operating power level.
The amplifier may therefore be operated at a higher ambient temperature than required by the P_Dmax formula
for a 3 Ω load.
The maximum ambient temperature depends on the heat sinking ability of the PCB system. The derating factor
for the PWP package is shown in the dissipation rating table (see page 4). Converting this to Θ_JA:
+ + + ń Θ_JA
1
Derating Factor
1
0.022
45°C W
(12)
To calculate maximum ambient temperatures, first consider that the numbers from the dissipation graphs are
per channel so the dissipated power needs to be doubled for two channel operation. Given Θ_JA, the maximum
allowable junction temperature, and the total internal dissipation, the maximum ambient temperature can be
calculated with the following equation. The maximum recommended junction temperature for the TPA0222 is
150°C. The internal dissipation figures are taken from the Power Dissipation vs Output Power graphs.
+ * T_A Max T_J Max Θ_JA P_D
(13)
+ * + 150 45(0.6 2) 96°C (15 dB crest factor)
NOTE:
Internal dissipation of 0.6 W is estimated for a 2-W system with 15 dB crest factor per channel.
TableS 4 and 5 show that for some applications no airflow is required to keep junction temperatures in the
specified range. The TPA0222 is designed with thermal protection that turns the device off when the junction
temperature surpasses 150°C to prevent damage to the IC. Tables 4 and 5 were calculated for maximum
listening volume without distortion. When the output level is reduced the numbers in the table change
significantly. Also, using 8-Ω speakers dramatically increases the thermal performance by increasing amplifier
efficiency.
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