TDA8922B NXP Semiconductors, TDA8922B Datasheet - Page 17

• Manufacturer Part Number: TDA8922B
• Description: The TDA8922B is a high efficiency class-D audio power amplifier with very lowdissipation
• Manufacturer: NXP Semiconductors

Philips Semiconductors
9397 750 13357
Preliminary data sheet
13.5 Heatsink requirements
13.6 Output current limiting
In some applications it may be necessary to connect an external heatsink to the
TDA8922B. 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
TDA8922B as a function of output power is given in
be derived as function of output power
The derating curves (given for several values of the R
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.
To guarantee the robustness of the class-D amplifier the maximum output current which
can be delivered by the output stage is limited. An advanced OverCurrent Protection
(OCP) is included for each output power switch.
When the current flowing through any of the power switches exceeds the defined internal
threshold of 5 A (e.g. in case of a short-circuit to the supply lines or a short-circuit across
the load) the maximum output current of the amplifier will be regulated to 5 A.
R
Fig 8. Derating curves for power dissipation as a function of maximum ambient
diss
th j a
(1) R
(2) R
(3) R
(4) R
(5) R
is determined by the efficiency ( ) of the TDA8922B. The efficiency measured in the
–
temperature.
=
th(j-a)
th(j-a)
th(j-a)
th(j-a)
th(j-a)
T
------------------------------------- -
j max
= 5 K/W.
= 10 K/W.
= 15 K/W.
= 20 K/W.
= 35 K/W.
P
diss
–
T
P
(W)
Rev. 01 — 1 October 2004
diss
amb
30
20
10
0
0
20
j
= 150 C is taken into account. From
(1)
(2)
(3)
(4)
(5)
Figure
40
18.
60
Figure
th(j-a)
2
80
T
amb
) are illustrated in
50 W class-D power amplifier
mbl469
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
19. The power dissipation can
( C)
100
TDA8922B
Figure 8
j(max)
Figure
which
the
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8. A