Datasheet

q
JA
+
1
Derating Factor
T
A
Max + T
J
Max * q
JA
P
Dmax
TPA2011D1
www.ti.com SLOS626A –DECEMBER 2009–REVISED MAY 2010
EFFICIENCY AND THERMAL INFORMATION
The maximum ambient operating temperature of the TPA2011D1 depends on the load resistance, power supply
voltage and heat-sinking ability of the PCB system. The derating factor for the YFF package is shown in the
dissipation rating table. Converting this to q
JA
:
(17)
Given q
JA
(from the Package Dissipation ratings table), the maximum allowable junction temperature (from the
Absolute Maximum ratings table), and the maximum internal dissipation (from Power Dissipation vs Output
Power figures) the maximum ambient temperature can be calculated with the following equation. Note that the
units on these figures are Watts RMS. Because of crest factor (ratio of peak power to RMS power) from 9–15
dB, thermal limitations are not usually encountered.
(18)
The TPA2011D1 is designed with thermal protection that turns the device off when the junction temperature
surpasses 150°C to prevent damage to the IC. Note that the use of speakers less resistive than 4-Ω (typ) is not
advisable. Below 4-Ω (typ) the thermal performance of the device dramatically reduces because of increased
output current and reduced amplifier efficiency. The Absolute Maximum rating of 3.2-Ω covers the manufacturing
tolerance of a 4-Ω speaker and speaker impedance decrease due to frequency. q
JA
is a gross approximation of
the complex thermal transfer mechanisms between the device and its ambient environment. If the q
JA
calculation
reveals a potential problem, a more accurate estimate should be made.
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