TPA0242

STEREO 2-W AUDIO POWER AMPLIFIER

WITH DC VOLUME CONTROL AND MUX CONTROL

SLOS287 – NOVEMBER 1999

26

POST OFFICE BOX 655303

APPLICATION INFORMATION

To calculate maximum ambient temperatures, first consider that the numbers from the dissipation graphs are

per channel so the dissipated heat needs to be doubled for two channel operation. Given

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 TPA0242 is

150

°C. The internal dissipation figures are taken from the Power Dissipation vs Output Power graphs.

T

+ 150 * 45(0.6

2)

(13)

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 TPA0242 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.

SE/BTL operation

The ability of the TPA0242 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 TPA0242, 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 TPA0242 is in the BTL mode. When SE/BTL is held high, the OUT–

amplifiers are in a high output impedance state, which configures the TPA0242 as an SE driver from LOUT+

input can be from a logic-level CMOS source or, more typically, from a resistor divider network as shown in

Figure 36.

ROUT+

21

R

MUX

RHPIN

RLINEIN

+

–

23

20

8

RIN

ROUT–

16

+

–

1 k

Ω

COUTR

330

µF

100 k

Ω

SE/BTL

15

100 k

Ω

VDD

Figure 36. TPA0242 Resistor Divider Network Circuit