Thermal Design. The IC power dissipation of the STK4142II at the IC-operated mode is 37.2W max. at load resistance 8 and 51.8W max. at load resistance 4 (simultaneous drive of 2 channels) for continuous sine wave as shown in Figure 1 and 2.
In an actual application where a music signal is used, it is impractical to estimate the power dissipation based on the con- tinuous signal as shown above, because too large a heat sink must be used. It is reasonable to estimate the power dissipa- tion as 1/10 Po max. (EIAJ).
That is, Pd = 23.6W at 8 , Pd = 28.2W at 4
Thermal resistance c-a of a heat sink for this IC power dissipation (Pd) is ﬁxed under conditions 1 and 2 shown below.
Condition 1: Tc = Pd × c-a + Ta 125°C...............................................
Ta : Speciﬁed ambient temperature
Tc : Operating substrate temperature
Condition 2: Tj= Pd × (c-a) + Pd/4 × (c-a) + Ta 150°C ....................
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 j-c is 2.6°C/W and Pd × (c-a + 2.6/4) + Ta 150°C
Thermal resistance c-a of a heat sink must satisfy ine-qualities (1) and (3).
Figure 3 shows the relation between Pd and c-a given from (1) and (3) with Ta as a parameter.
The thermal resistance of a heat sink is obtained when the ambient temperature speci- ﬁed for a stereo ampliﬁer is 50°C. Assuming VCC = ±26V, RL = 8 , VCC = ±22V, RL = 4 , RL = 8 : Pd1 = 23.6W at 1/10 Po max. RL = 4 : Pd2 = 28.2W at 1/10 Po max. The thermal resistance of a heat sink is obtained from Figure 3.
RL = 8 : c-a1 = 3.18°C/W RL = 4 : c-a2 = 2.66°C/W
Tj when a heat sink is used is obtained from
RL = 8 : Tj = 140.4°C
RL = 4 : Tj = 143.4°C
The STK4102II series (STK4142II) and STK4101V series (high-grade type) are pin-compatible in the out- put range of 6W to 50W and enable easy design.
•Small-sized package whose pin assignment is the same as that of the STK4101II series
•Built-in muting circuit to cut off various kinds of pop noise
•Greatly reduced heat sink due to substrate temperature 125°C guaranteed
•Excellent cost performance
Interrupter Circuit STK 4142 Comparison / Similar / Equivalent is : STK 4192