Datasheet

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SLOS327C − AUGUST 2000 − REVISED MAY 2001
22
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
SE/BTL
operation
The ability of the TPA0172 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 TPA0172, two separate amplifiers drive OUT+ and OUT−. The SE/BTL
input controls the
operation of the follower amplifier that drives LOUT− and ROUT−. When SE/BTL
is held low, the amplifier is
on and the TPA0172 is in the BTL mode. When SE/BTL
is held high, the OUT− amplifiers are in a high output
impedance state, which configures the TPA0172 as an SE driver for LOUT+ and ROUT+. 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 (see
recommended operating conditions for levels) or, more typically, from a resistor divider network as shown in
Figure 25.
The SE/BTL
pin also selects the audio input and gain registers. When SE/BTL is held low, the RLINEIN input
is selected and the BTL gain register values are used to set the gain of the input signal. When SE/BTL
is held
high, the RHPIN input is selected and the SE gain register values are used to set the gain. Table 5 shows the
operation of the SE/BTL
input pin in selecting different modes of operation.
Table 5. SE/BTL
Operation
SE/BTL INPUT GAIN REGISTER OUTPUT
Low Line BTL BTL
High Headphone SE SE
The external SE/BTL pin may also be disabled and its function controlled through the I
2
C interface. Refer to the
I
2
C interface section.
ROUT+ 12
R
MUX
RHPIN
RLINEIN
+
−
18
17
9 RIN
ROUT− 14
+
−
1 kΩ
C
OUTR
330 µF
100 kΩ
SE/BTL
11
100 kΩ
V
DD
Figure 25. TPA0172 Resistor Divider Network Circuit