STK400-070 Sanyo Semiconductor Corporation, STK400-070 Datasheet - Page 6

• Manufacturer Part Number: STK400-070
• Description: af Power Amplifier (40W+40W+40W)
• Manufacturer: Sanyo Semiconductor Corporation

External Circuit Diagram
Heatsink Design Considerations
The heatsink thermal resistance, c-a, required to dissipate
the STK400-070 device total power dissipation, Pd, is
determined as follows:
Condition 1: IC substrate temperature not to exceed
125 C.
where Ta is the guaranteed maximum ambient tempera-
ture.
Condition 2: Power transistor junction temperature, Tj, not
to exceed 150 C.
where N is the number of power transistors and j-c is the
power transistor thermal resistance per transistor. Note
that the power dissipated per transistor is the total, Pd,
divided evenly among the N power transistors.
Expressions (1) and (2) can be rewritten making c-a the
subject.
The heatsink required must have a thermal resistance that
simultaneously satisfies both expressions.
Pd
Pd
c-a < (125 Ta)/Pd ............................................. (1)
c-a < (150 Ta)/Pd
c-a + Ta < 125 C ........................................ (1)
c-a + Pd/N
j-c + Ta < 150 C ................. (2)
j-c/N .............................. (2)
STK400-070
The heatsink thermal resistance can be determined from
(1) and (2) once the following parameters have been
defined.
• Supply voltage
• Load resistance
• Guaranteed maximum ambient temperature
The total device power dissipation when STK400-070
V
nal, is a maximum of 93W, as shown in Figure 1.
When estimating the power dissipation for an actual audio
signal input, the rule of thumb is to select Pd correspond-
ing to 1/10 P
sine wave input. For example, from Figure 1,
The STK400-070 has 6 power transistors, and the thermal
resistance per transistor, j-c, is 1.7 C/W. If the guaran-
teed maximum ambient temperature, Ta, is 50 C, then the
required heatsink thermal resistance, c-a, is:
From expression (1) : c-a < (125 50)/56.5
From expression (2) : c-a < (150 50)/56.5 1.7/6
Therefore, to satisfy both expressions, the required heat-
sink must have a thermal resistance less than 1.32 C/W.
CC
Pd = 56.5W (for 1/10 P
= 30V and R
O
max (within safe limits) for a continuous
L
= 6 , for a continuous sine wave sig-
O
< 1.32
< 1.48
max = 4W)
No. 4598—6/9