STK402-090 Sanyo, STK402-090 Datasheet - Page 4

• Manufacturer Part Number: STK402-090
• Description: Two-Channel Class AB Audio Power Amplifier IC 50 W + 50 W
• Manufacturer: Sanyo

Thermal Design Example
The thermal resistance, c-a of the required heat sink for the power dissipation, Pd, within the hybrid IC is determined as
follows.
Condition 1: The IC substrate temperature, Tc, must not exceed 125°C.
Condition 2: The junction temperature, Tj, of each power transistor must not exceed 150°C.
However, the power dissipation, Pd, for the power transistors shall be allocated equally among the N transistors.
The following inequalities results from solving equations (1) and (2) for c-a.
Values that satisfy these two inequalities at the same time represent the required heat sink thermal resistance.
When the following specifications have been stipulated, the required heat sink thermal resistance can be determined from
formulas (1)’ and (2)’.
[Example]
When the IC supply voltage, V
72 W for a continuous sine wave signal at 1 kHz, according to the Pd – P
For the music signals normally handled by audio amplifiers, a value of 1/8 P
of the power dissipation based on this type of continuous signal. (Note that the factor used may differ depending on the
safety standards used.)
That is:
The number of power transistors in the audio amplifier block of these hybrid ICs, N, is 4, and the thermal resistance per
transistor is 2.2°C/W. Therefore, the required heat sink thermal resistance for a guaranteed ambient temperature of 50°C
will be as follows.
Therefore, 1.53°C/W is the required heat sink thermal resistance.
Note that this thermal design example assumes the use of a constant-voltage power supply, and is therefore not a verified
design for any particular user's end product.
Pd
Pd
• Supply voltage — V
• Load resistance value — RL
• Guaranteed ambient temperature — Ta
Pd = 48 W (When 1/8 P
From formula (1)’
From formula (2)’
c – a < (125 – Ta) /Pd . . . . . . . . . . . . . . . . . . (1)’
c – a < (150 – Ta) /Pd – j – c/N . . . . . . . . . (2)’
c – a + Ta < 125°C . . . . . . . . . (1)
c – a + Pd/N
Ta: Guaranteed ambient temperature for the end product.
N: Number of power transistors
c-a: Thermal resistance per power transistor
CC
j – c + Ta < 150°C . . . . . . . . . (2)
O
CC
max = 6.25 W)
, is ±32 V and R
c – a < (125 – 50) /48
c – a < (150 – 50) /48 – 2.2/4
< 1.53
< 1.56
L
is 6 Ω, the IC internal power dissipation, Pd, will be a maximum of
STK402-090
O
characteristics.
O
max is generally used for Pd as an estimate
No. 7065-4/5