STK4412 Datasheet, PDF (6/7 Pages) Sanyo Semicon Device – 2-Channel AF Power Amplifier (20W+20W min, THD = 1.0%)

STK4412
Sample Application Circuit (protection circuit and muting circuit)
Thermal Design
The IC power dissipation of the STK4412 at the IC-oper-
ated mode is 26.8W max. at load resistance 8Ω (simulta-
neous drive of 2 channels) for continuous sine wave as
shown in Figure 1.
In an actual application where a music signal is used, it is
impractical to estimate the power dissipation based on the
continuous signal as shown right, because too large a heat
sink must be used. It is reasonable to estimate the power
dissipation as 1/10 Po max. (EIAJ).
That is, Pd = 17.2W at 8Ω
Thermal resistance θc-a of a heat sink for this IC power
dissipation (Pd) is fixed under conditions 1 and 2 shown
below.
Output power, Po - W
Figure 1. STK4412 Pd – Po (R_L = 8Ω)
Condition 1: T_C = Pd × θc-a + Ta ≤ 125°C .............................................. (1)
where Ta : Specified ambient temperature
T_C : Operating substrate temperature
Condition 2: Tj = Pd × (θc-a) + Pd/4 × (θj-c) + Ta ≤ 150°C.................... (2)
where Tj : Junction temperature of power transistor
Assuming that the power dissipation is shared equally among the four power transistors (2 channels × 2), thermal resis-
tance θj-c is 3.6°C/W and
Pd × (θc-a + 3.6/4) + Ta ≤ 150°C........................................ (3)
No. 2860—6/7