STK400-100 Просмотр технического описания (PDF) - SANYO -> Panasonic
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STK400-100 Datasheet PDF : 6 Pages
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STK400-030
Heatsink Design Considerations
The heatsink thermal resistance, θc-a, required to cover
the hybrid IC’s total power dissipation, Pd, is determined
as follows:
Condition 1: Hybrid IC’s substrate temperature not to
exceed 125°C.
Pd × θc-a + Ta < 125°C ........................................ (1)
where Ta is the guaranteed maximum ambient tempera-
ture.
Condition 2: Power transistor junction temperature, Tj, not
to exceed 150°C.
Pd × θc-a + Pd/N × θj-c + Ta < 150°C ................. (2)
where N is the number of power transistors and θj-c is the
thermal resistance per power 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 θc-a the
subject.
θc-a < (125 − Ta)/Pd ............................................. (1)′
θc-a < (150 − Ta)/Pd − θj-c/N .............................. (2)′
The heatsink required must have a thermal resistance that
simultaneously satisfies both expressions.
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
: VCC
: RL
: Ta
The total device power dissipation when hybrid IC’s VCC
= ±23V and RL = 6Ω, for a continuous sine wave signal, is
a maximum of 55W, as is in Pd-PO graph.
When estimating the power dissipation for an actual audio
signal input, the rule of thumb is to select Pd correspond-
ing to 1/10 PO max (within safe limits) for a continuous
sine wave input. For example,
Pd = 31W (for 1/10 PO max = 2W)
The hybrid IC has 6 power transistors, and the thermal
resistance per transistor, θj-c, is 2.1°C/W. If the guaran-
teed maximum ambient temperature, Ta, is 50°C, then the
required heatsink thermal resistance, θc-a, is:
From expression (1)′: θc-a < (125 − 50)/31
< 2.41
From expression (2)′: θc-a < (150 − 50)/31 − 2.1/6
< 2.87
Therefore, to satisfy both expressions, the required heat-
sink must have a thermal resistance less than 2.41°C/W.
Similarly, when hybrid IC’s VCC = ±19V and RL = 3Ω:
Pd = 36W (for 1/10 PO max = 2W)
From expression (1)′: θc-a < (125 − 50)/36
< 2.08
From expression (2)′: θc-a < (150 − 50)/36 − 2.1/6
< 2.42
Therefore, to satisfy both expressions, the required heat-
sink must have a thermal resistance less than 2.08°C/W.
This heatsink design example is based on a constant-volt-
age egulated power supply, and should be verified within
your specific set environment.
Output power per channel, PO /ch - W
Output power per channel, PO /ch - W
No. 5703—4/6
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