TDA8922BTH View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TDA8922BTH

2×50 W class-D power amplifier

Philips Electronics 

Philips Semiconductors

TDA8922B

2 × 50 W class-D power amplifier

13.5 Heatsink requirements

In some applications it may be necessary to connect an external heatsink to the

TDA8922B. Limiting factor is the 150 °C maximum junction temperature Tj(max) which

cannot be exceeded. The expression below shows the relationship between the maximum

allowable power dissipation and the total thermal resistance from junction to ambient:

Rth( j – a)

=

T-----j--(--m----a--x---)---–-----T----a--m----b-

Pdiss

Pdiss is determined by the efficiency (η) of the TDA8922B. The efficiency measured in the

TDA8922B as a function of output power is given in Figure 19. The power dissipation can

be derived as function of output power Figure 18.

The derating curves (given for several values of the Rth(j-a)) are illustrated in Figure 8. A

maximum junction temperature Tj = 150 °C is taken into account. From Figure 8 the

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.

30

Pdiss

(W)

(1)

20

mbl469

(2)

10

(3)

(4)

(5)

0

0

20

40

60

80

100

Tamb (°C)

(1) Rth(j-a) = 5 K/W.

(2) Rth(j-a) = 10 K/W.

(3) Rth(j-a) = 15 K/W.

(4) Rth(j-a) = 20 K/W.

(5) Rth(j-a) = 35 K/W.

Fig 8. Derating curves for power dissipation as a function of maximum ambient

temperature.

13.6 Output current limiting

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.

9397 750 13357

Preliminary data sheet

Rev. 01 — 1 October 2004

© Koninklijke Philips Electronics N.V. 2004. All rights reserved.

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