TPA6030A4 Datasheet, PDF (20/27 Pages) Texas Instruments – 3-2 STEREO AUDIO POWER AMPLIFIER WITH ADVANCED DC VOLUME CONTROL

TPA6030A4
SLOS395A – DECEMBER 2002 – REVISED JANUARY 2003
VCC
VO(PP)
–3 dB
www.ti.com
CC
RL
VO(PP)
fc
Figure 25. Single-Ended Configuration and Frequency Response
Bridge-tying the outputs in a typical computer audio, or LCD TV or multimedia LCD monitor application drastically increases
output power. For example, if an amplifier in a single-ended configuration was capable of outputting a maximum of 250 mW
for a given load with a supply voltage of 12 V, then that same amplifier would be able to output 1 W of power in a BTL
configuration with the same supply voltage and load. In addition to the increase in output power, the BTL configuration does
not suffer from the same low frequency issues that plague the single-ended configuration. In a BTL configuration, there
is no need for an output capacitor to block dc, so no unwanted filtering occurs. In addition, the BTL configuration saves
money and space, as the dc-blocking capacitors needed for single-ended operation are large and expensive. For example,
with an 8-Ω load in SE operation, the user needs a capacitor of 995 µF to obtain a lower cutoff frequency of 20 Hz. This
capacitor would be very expensive and very large.
Single-Ended Operation
Figure 25 shows a Class-AB audio power amplifier in an SE configuration. In SE mode, the load is driven from the primary
amplifier for each channel (Rout+ and Lout+, terminals 27 and 16 respectively). The amplifier switches from BTL to SE
mode when the SE/BTL pin is held high⁽¹⁾. This puts the negative outputs of the amplifier into a high impedance state, and
reduces the amplifier’s gain according to the voltage applied to SEDIFF and SEMAX.
SE/BTL Operation
The ability of the TPA6030A4 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 an external headphone must be accommodated. The follower amplifiers that drive
Rout– and Lout– (terminals 1 and 14) are controlled by the SE/BTL input (terminal 26). When SE/BTL is held low⁽¹⁾, the
amplifiers are on and the TPA6030A4 is in the BTL mode. When SE/BTL is held high⁽¹⁾, only the positive output amplifiers
are on. The negative outputs enter a high impedance state, which configures the TPA6030A4 as an SE driver from the
Rout+ and Lout+ outputs (terminals 27 and 16). Control of the SE/BTL input can be from a separate voltage source or, more
typically, from a resistor divider network. See Figure 26 for an example of a resistor divider network.
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 parallel combination of R5 and R7 (see Figure 22) pulls the SE/BTL pin low⁽¹⁾, causing the device to
operate in BTL mode. When a plug is inserted, the 1-kΩ resistor is disconnected and the SE/BTL input is pulled high⁽¹⁾.
When the input goes high⁽¹⁾, the negative output amplifiers go into a state of high impedance, essentially open circuiting
the speaker. The positive output amplifiers then drive through the output capacitor (C_O) into the headphone jack.
IN2/IN1 Operation
The TPA6030A4 has the ability to switch between the two input sources. Those sources are dubbed IN2 and IN1. There
is no functional difference between the two inputs. Both perform equally well with any audio signal (provided that signal
is within the specified limits set forth earlier in this document). However, only one input at a time is allowed through to the
output. IN2/IN1 (terminal 26) controls which input is allowed into the amplifier. As with SE/BTL, IN2/IN1 can be controlled
by either a separate voltage source or, more typically, from a resistor divider network. See Figure 26 for an example of a
resistor divider network.
(1) _{Refer to the table entiled Recommended Operating Conditions.}
20