SA7454
than:
(150°C－50°C)/6W＝16.7°C/W
For HSIP-9 package, the die-to-package thermal resistance is Rth(j-c) = 8°C/W，then the package-to-ambient
thermal resistance should be lower than 8.7°C/W. So we need heat sink to reduce the package-to-ambient
thermal resistance.
For DIP-18IH-300-2.54 package, the die-to-package thermal resistance is Rth(j-c) = 15°C/W，then the
package-to-ambient thermal resistance should be lower than 1.7°C/W，that will make heat sinking difficult, in
addition, DIP-18IH-300-2.54 can not add effective heat sink, so we need to reduce the power dissipation by
reducing load. For example, with a 8Ω load, it can develop up to 3W of internal power dissipation, and the
package-to-ambient thermal resistance should be lower than:
(150°C－50°C)/3W－15°C/W＝18.3°C /W
The thermal requirements can become more difficult when SA7454 is driving a reactive load. As a general rule,
the power dissipation of an amplifier driving a 60º reactive load (usually considered to be a worst-case
loudspeaker load) will be roughly that of the same amplifier driving the resistive part of that load. For example, a
loudspeaker may at some frequency have an impedance with a magnitude of 8Ω and a phase angle of 60º. The
real part of this load will then be 4Ω, and the amplifier power dissipation equal to the power dissipation with a 4Ω
load.
TYPICAL APPLICATION CIRCUIT
HANGZHOU SILAN MICROELECTRONICS CO.,LTD
Http://www.silan.com.cn
REV:1.0
2008.10.21
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