STK4172II Datasheet, PDF (8/8 Pages) Sanyo Semicon Device – AF Power Amplifier (Split Power Supply) (40W + 40W min, THD = 0.4%)

STK4172II
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 = 35W at 8Ω, Pd = 49W at 4Ω
Thermal resistance θc-a of a heat sink for this IC power dissipation (Pd) is fixed under conditions 1 and 2 shown below.
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 (2 channels × 2), thermal resis-
tance θj-c is 1.8°C/W and
Pd × (θc-a + 1.8/4) + Ta ≤ 150°C........................................ (3)
Thermal resistance θc-a of a heat sink must satisfy ine-
qualities (1) and (3).
Figure 3 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 V_CC = ±32V, R_L = 8Ω,
V_CC = ±29V, R_L = 4Ω,
R_L = 8Ω : Pd1 = 35W at 1/10 Po max.
R_L = 4Ω : Pd2 = 49W at 1/10 Po max.
The thermal resistance of a heat sink is
obtained from Figure 3.
R_L = 8Ω : θc-a1 = 2.15°C/W
R_L = 4Ω : θc-a2 = 1.53°C/W
Tj when a heat sink is used is obtained from
(3).
R_L = 8Ω : Tj = 141°C
R_L = 4Ω : Tj = 147°C
IC Power dissipation, Pd - W
Figure 3. STK4172II θc-a – Pd
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 Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on SANYO ELECTRIC CO.,
LTD., its affiliates, subsidiaries and distributors or any of their officers and employees, jointly or severally.
s Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for volume production. SANYO
believes information herein is accurate and reliable, but no guarantees are made or implied regarding its use or any infringements of
intellectual property rights or other rights of third parties.
This catalog provides information as of July, 1997. Specifications and information herein are subject to change without notice.
No. 2323—8/8