Philips TDA1561Q Datasheet page 7

Philips Semiconductors
2 23 W high efficiency car radio power
amplifier
Heatsink design
There are two parameters that determine the size of the
heatsink. The first is the rating for the virtual junction
temperature and the second is the ambient temperature at
which the amplifier must still deliver its full power in the
BTL mode.
With a conventional BTL amplifier, the maximum power
dissipation with a music-like signal (at each amplifier) will
be approximately two times 5 W. At a virtual junction
temperature of 150 C and a maximum ambient
temperature of 60 C, R
R = 0.2 K/W, the thermal resistance of the heatsink
th(c-h)
150 60 –
should be: --------------------- - 1.3
–
2 5
Compared to a conventional BTL amplifier, the TDA1561Q
has a higher efficiency. The thermal resistance of the
heatsink should be:
150 60
–
1.7 1.3 0.2
--------------------- - – –
2 5
1997 Aug 14
= 1.3 K/W and
th(vj-c)
0.2 7.5 K/W
– =
13.8 K/W
=
handbook, halfpage
OUT 1 OUT 1
3.6 K/W
0.6 K/W
0.1 K/W
Fig.3 Thermal equivalent resistance network.
7
Preliminary specification
TDA1561Q
virtual junction
OUT 2 OUT 2
3.6 K/W
3.6 K/W
0.6 K/W
MGC424
case
3.6 K/W