Datasheet

TPA0202
2-W STEREO AUDIO POWER AMPLIFIER
SLOS205B – FEBRUARY 1998 – REVISED DECEMBER 2000
40
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
APPLICATION INFORMATION
headroom and thermal considerations (continued)
T
A
Max T
J
Max Θ
JA
P
D
150 45
(
0.6 2
)
96°C
(
15 dB headroom, 0 CFM
)
(20)
NOTE:
Internal dissipation of 0.6 W is estimated for a 2-W system with 15 dB headroom per channel.
Table 4 shows that for some applications no airflow is required to keep junction temperatures in the specified
range. The TPA0202 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 was 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.
junction temperature measurement
Characterizing a PCB layout with respect to thermal impedance is very difficult, as it is usually impossible to
know the junction temperature of the IC in question. The TPA0202 terminal 2 (TJ) sources a current proportional
to the junction temperature. The circuit internal to TJ is shown in Figure 70.
5R
TJ
V
DD
R
R
Figure 70. TJ Terminal Internal Circuit
Connect an ammeter between TJ and ground to measure the current. As the resistors have a tolerance of ±20%,
this measurement must be calibrated on each device. The intent of this function is in characterization of the PCB
and end equipment and not a real-time measurement of temperature. Typically a 25°C reading is –120 µA for
a 3.3-V supply and –135 µA for a 5-V supply. The slope is approximately 0.25 µA/°C for both V
DD
= 3.3 V and
V
DD
= 5 V. To reduce quiescent current, do not ground TJ in normal operation. It can be connected to V
DD
or
left floating as it has a resistor connected across the base-emitter junction.