Philips Semiconductors
Preliminary specification
Multi-purpose power amplifier
TDA8580J
For BTL application at Vp = 24 V, RL = 8 Ω and Po at
THD = 0.5% (see Fig.15), the Average Listening
Level (ALL) for music power without distortion yields:
EXAMPLE
Measured or given values:
Vp = 24 V
23
Po(ALL)
=
= 1.45 W.
--------------
RL = 8 Ω (2 × BTL)
15.85
Measured worst case Pd (sine wave) = 32 W
Tj(max) = 150oC
Tamb(max) = 60oC
Table 2 Pd as a function of headroom (music signals) for
Po = 2 × 23 W (THD = 0.5%).
HEADROOM
Pd
Rth(j-c) = 1.5 K/W
0 dB
32 W
16 W
Tj(max) – T
Rth(hs)
=
amb(max) – R
--------------------------------------------------
th(j – c)
12 dB
Pd
150 – 60
----------------------
32
=
– 1.5 = 1.3 K/W
So for the average music listening level a total power
dissipation of 16 W can be used for calculating the
optimum heat sink thermal resistance.
Table 3 Heatsink thermal resistance as a function of
headroom for Po = 2 × 23 W (THD = 0.5%).
Heatsink calculation
HEAD ROOM
Pd
32 W
16 W
Rth(hs)
The measured thermal resistance of this package Rth(j-c) is
a maximum of 1.5 K/W. For a maximum ambient
temperature of 60oC the required heatsink thermal
resistance can be calculated as shown in the following
example.
0 dB
1.3 K/W
12 dB
4.12 K/W
2000 Apr 18
17
NXP [ NXP ]
