AN10436 PHILIPS [NXP Semiconductors], AN10436 Datasheet - Page 37

• Manufacturer Part Number: AN10436
• Description: TDA8932B/33(B) Class-D audio amplifier
• Manufacturer: PHILIPS [NXP Semiconductors]

NXP Semiconductors
AN10436_1
Application note
Airflow inside enclosure
At a set level the airflow inside the enclosure will be limited compared to the situation in
free air natural convection. The airflow and other heat sources close to the amplifier will
influence the temperature significantly. Therefore it is always recommended (and the
responsibility of the set maker) to check the temperature behavior in the final environment
of the amplifier.
Remark: The TDA8932B/33(B) amplifier with the thermal foldback feature will never
cause audio interruption (audio holes) due to the limited airflow and the limited presence
of other heat sources close to the amplifier. Therefore this thermal foldback feature will
improve the reliable of the amplifier application under extreme temperature conditions
because the device itself will always stay within the Safe Operating Area (SOA).
Thermal resistance
Measured thermal resistance of both the SO32 and the HTSSOP32 reference design can
be found in
Thermal via’s
Thermal via’s should be applied for an optimum heat flow to other layers of the PCB to
reduce the R
the package for the SO32 package (see PCB layout
Remark: Do not use via’s with web construction, as they will have a high thermal
resistance.
Thermal calculations
To estimate the maximum junction temperature,
Where:
Example:
Estimation of the junction temperature at P
Power dissipation P = 2.5 W (see
junction temperature at T
(approx.)
At a P
and therefore reduce the long-term output power. See
a function of time, when the TF becomes active. The major benefit of the TF feature is that
the amplifier is not switched off when it reaches the maximum junction temperature.
Remark: Lifetime is guaranteed because the TDA8932B/33(B) stays within the safe
operating area due to the TF feature.
T
j max
T
P = power dissipation in U1 (W) (see
R
(
amb
th(j−a)
)
rated
≈
= ambient temperature (°C)
T
= thermal resistance junction ambient (K/W)
(Equation
amb
= 2 × 25 W in 4 Ω the TF becomes active. The TF will gradually reduce the gain
Section
th(j−a)
+
R
th j a
. The thermal via’s should be placed close to corner leads and beyond
(
5.3.
22), staying below the TF threshold level of 140 °C.
–
Rev. 01 — 12 December 2007
)
⋅
P
amb
= 25 °C and R
Figure
Figure 50
47) at P
rated
th(j−a)
TDA8932B/33(B) Class-D audio amplifier
(for FTC requirements).
Equation 22
= 44 K/W, will be T
rated
or
Figure
Section
= 2 × 15 W in 4 Ω. The estimated
Section 5.3
61, P versus P
3.12).
can be used:
for the output power as
j(max)
AN10436
© NXP B.V. 2007. All rights reserved.
= 135 °C
O
)
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