TPA0312_16 Datasheet, PDF (27/37 Pages) Texas Instruments – 2.6-W STEREO AUDIO POWER AMPLIFIER WITH FOUR SELECTABLE GAIN SETTINGS AND MUX CONTROL

TPA0312
www.ti.com
SLOS335A – DECEMBER 2000 – REVISED OCTOBER 2004
Table 4 and Table 5 show that for some applications no airflow is required to keep junction temperatures in the
specified range. The TPA0312 is designed with thermal protection that turns the device off when the junction
temperature surpasses 150°C to prevent damage to the IC. Table 4 and Table 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.
SE/BTL OPERATION
The ability of the TPA0312 to easily switch between BTL and SE modes is one of its most important cost-saving
features. This feature eliminates the requirement for an additional headphone amplifier in applications where
internal stereo speakers are driven in BTL mode but external headphone or speakers must be accommodated.
Internal to the TPA0312, two separate amplifiers drive OUT+ and OUT-. The SE/BTL input (terminal 15) controls
the operation of the follower amplifier that drives LOUT- and ROUT- (terminals 9 and 16). When SE/BTL is held
low, the amplifier is on and the TPA0312 is in the BTL mode. When SE/BTL is held high, the OUT- amplifiers are
in a high-output impedance state, which configures the TPA0312 as an SE driver from LOUT+ and ROUT+
(terminals 4 and 21). I_DD is reduced by approximately one-half in SE mode. Control of the SE/BTL input can be
from a logic-level CMOS source or, more typically, from a resistor divider network as shown in Figure 42.
20 RHPIN
23 RLINEIN
R
MUX
Volume
Control
−
+
8 RIN
Volume
Control
−
+
ROUT+ 21
V_DD
ROUT− 16
100 kΩ
SE/BTL 15 ^{100 kΩ}
C_OUTR
330 µF
1 kΩ
Figure 42. TPA0312 Resistor Divider Network Circuit
Using a readily available 1/8-in. (3,5-mm) stereo headphone jack, the control switch is closed when no plug is
inserted. When closed, the 100-kΩ/1-kΩ divider pulls the SE/BTL input low. When a plug is inserted, the 1-kΩ
resistor is disconnected and the SE/BTL input is pulled high. When the input goes high, the OUT- amplifier is
shut down causing the speaker to mute (virtually open-circuits the speaker). The OUT+ amplifier then drives
through the output capacitor (C_O) into the headphone jack.
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