STK4048XI(1997) データシートの表示（PDF） - SANYO -> Panasonic

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STK4048XI
(Rev.:1997)

AF Power Amplifier (Split Power Supply) (150W min, THD = 0.008%)

SANYO -> Panasonic 

STK4048XI

Thermal Design

The IC power dissipation of the STK4048XI at the IC-

operated mode is 100W max. at load resistance 8Ω 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 = 65W 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. STK4048XI Pd – Po (RL = 8Ω)

Condition 1: Tc = Pd × θc-a + Ta ≤ 125°C .............................................. (1)

where Ta : Specified ambient temperature

Tc : 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, thermal resistance θj-c is

1.2°C/W and

Pd × (θc-a + 1.2/4) + Ta ≤ 150°C........................................ (3)

Thermal resistance θc-a of a heat sink must satisfy ine-

qualities (1) and (3).

Figure 2 shows the relation between Pd and θc-a given

from (1) and (3) with Ta as a parameter.

[Example] The thermal resistance of a heat sink is

obtained when the ambient temperature speci-

fied for a stereo amplifier is 50°C.

Assuming VCC = ±60V, RL = 8Ω,

RL = 8Ω : Pd = 65W at 1/10 Po max.

The thermal resistance of a heat sink is

obtained from Figure 2.

RL = 8Ω : θc-a1 = 1.15°C/W

Tj when a heat sink is used is obtained from

(3).

RL = 8Ω : Tj = 144.3°C

IC Power dissipation, Pd - W

Figure 2. STK4048XI θc-a – Pd

This design is based on the use of a constant-voltage regulated power supply. Pd differs when a transformer power supply

is used. Redesign must be made based on Pd that suits the regulation of each transformer.

No. 2909—7/8

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