APA2068 Datasheet, PDF (23/27 Pages) Anpec Electronics Coropration – Stereo 2.6W Audio Power Amplifier (with DC_Volume Control)

APA2068
Application Descriptions (Cont.)
Thermal Pad Considerations (Cont.)
design issues are not properly addressed, the
APA2068 4Ω will go into thermal shutdown when
driving a 4Ω load.
The thermal pad on the bottom of the APA2068 should
be soldered down to a copper pad on the circuit board.
Heat can be conducted away from the thermal pad
through the copper plane to ambient. If the copper plane
is not on the top surface of the circuit board, 8 to 10
vias of 13 mil or smaller in diameter should be used to
thermally couple the thermal pad to the bottom plane.
internal dissipation figures are taken from the Power
Dissipation vs. Output Power graphs.
TAMax = TJMax -θJAPD
(16)
150 - 45(0.8*2) = 78°C
The APA2068 is designed with a thermal shutdown
protection that turns the device off when the junction
temperature surpasses 150°C to prevent damaging the
IC.
For good thermal conduction, the vias must be plated
through and solder filled. The copper plane used to
conduct heat away from the thermal pad should be as
large as practical.
If the ambient temperature is higher than 25°C, a larger
copper plane or forced-air cooling will be required to
keep the APA2068 junction temperature below the
thermal shutdown temperature (150°C). In higher
ambient temperature, higher airflow rate and/or larger
copper area will be required to keep the IC out of
thermal shutdown.
Thermal Considerations
Linear power amplifiers dissipate a significant amount
of heat in the package under normal operating
conditions.
To calculate maximum ambient temperatures, first
consideration is that the numbers from the Power
Dissipation vs. Output Power graphs are per
channel values, so the dissipation of the IC heat needs
to be doubled for two-channel operation. Given θJA, the
maximum allowable junction temperature (TJMAX), and
the total internal dissipation (PD), the maximum
ambient temperature can be calculated with the
following equation. The maximum recommended
junction temperature for the APA2068 is 150°C. The
Copyright © ANPEC Electronics Corp.
23
Rev. A.2 - Jul., 2005
www.anpec.com.tw