www.ti.com

SE/BTL OPERATION

ROUT+

21

R

MUX

RHPIN

RLINEIN

+

−

23

20

8

RIN

ROUT−

16

+

−

1 k

Ω

330

µF

100 k

Ω

SE/BTL

15

100 k

Ω

32-Step

Volume

Control

32-Step

Volume

Control

TPA0142

SLOS248E – JUNE 1999 – REVISED SEPTEMBER 2004

The ability of the TPA0142 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.

Two separate internal 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 device is in the

BTL mode. When SE/BTL is held high, the OUT– amplifiers are in a high output-impedance state, which

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 38.

Figure 38. TPA0142 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-k

Ω/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, muting the speaker (virtually open-circuits the speaker). The OUT+ amplifier then drives through the

26