TDA8920B NXP Semiconductors, TDA8920B Datasheet - Page 17

• Manufacturer Part Number: TDA8920B
• Description: The TDA8920B is a high efficiency class-D audio power amplifier with very lowdissipation
• Manufacturer: NXP Semiconductors

Philips Semiconductors
TDA8920B_2
Product data sheet
13.5 Heatsink requirements
If two or more class-D amplifiers are used in the same audio application, it is strongly
recommended that all devices run at the same switching frequency. This can be realized
by connecting all OSC pins together and feed them from an external central oscillator.
Using an external oscillator it is necessary to force pin OSC to a DC-level above SGND for
switching from the internal to an external oscillator. In this case the internal oscillator is
disabled and the PWM modulator will be switched on the external frequency. The
frequency range of the external oscillator must be in the range as specified in the
switching characteristics; see
In an application circuit:
In some applications it may be necessary to connect an external heatsink to the
TDA8920B. Limiting factor is the 150 C maximum junction temperature T
cannot be exceeded. The expression below shows the relationship between the maximum
allowable power dissipation and the total thermal resistance from junction to ambient:
P
TDA8920B as a function of output power is given in
be derived as a function of output power (see
The derating curves (given for several values of R
A maximum junction temperature T
maximum allowable power dissipation for a given heatsink size can be derived or the
required heatsink size can be determined at a required dissipation level.
R
•
•
diss
th j a
Internal oscillator: R
External oscillator: connect the oscillator signal between pins OSC and SGND; R
and C
–
is determined by the efficiency ( ) of the TDA8920B. The efficiency measured in the
=
OSC
T
----------------------------------- -
j max
removed
P
diss
–
T
Rev. 02 — 07 November 2005
amb
OSC
connected between pin OSC and V
Section
j
= 150 C is taken into account. From
12.1.
Figure
th(j-a)
Figure
20).
2
) are illustrated in
100 W class-D power amplifier
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
21. The power dissipation can
SSA
TDA8920B
Figure
Figure 8
j(max)
which
8.
the
17 of 34
OSC
(5)