APL5525 查看數據表（PDF） - Anpec Electronics
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APL5525 Datasheet PDF : 17 Pages
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APL5525/5526
Application Information
Thermal Protection
Thermal protection limits total power dissipation in the
APL5538. When the junction temperature exceeds
TJ=+150°C, the thermal sensor generate a logic sig-
nal to turn off the pass transistor and let IC to cool.
When the IC’s junction temperature cools by 10°C,
the thermal sensor will turn the pass transistor on again,
resulting in a pulsed output during continuous thermal
protection. Thermal protection is designed to protect
the IC in the event of fault conditions. For continual
operation, do not exceed the absolute maximum junc-
tion temperature rating of TJ=+150°C.
heat into ambient air. The vias are recommended to
have proper size to retain solder, helping heat
conduction.
102 mil
118 mil
SOP-8-P
Thermal
Die pad
Top
ground
pad
Operating Region and Power Dissipation
The thermal resistance of the case and circuit board,
ambient and junction air temperature, and the rate of
air flow all control the APL5538 maximum power
dissipation. The power dissipation across the device
is P = IOUT (VIN-VOUT). The maximum power dissipation
is:
PMAX = (TJ-TA) / (θJB +θBA )
where TJ-TA is the temperature difference between the
junction and ambient air.
θJB is the thermal resistance of the package, θBA is the
thermal resistance through the printed circuit board,
copper traces, and other materials to the surrounding
air. The GND pin provides an electrical connection to
ground and channeling heat away. Connect the GND
pin to ground using a large pad or ground plane as a
heat sink, it can improve maximize thermal dissipation.
Ambient
Air
Vias
Figure 1
Internal
ground
plane
Printed
circuit
board
Figure 2 shows a board layout using the SOP-8-P
package. The demo board is made of FR-4 material
and is a two-layer PCB.
See figure 1. The SOP-8-P utilizes a bottom thermal
pad to minimize the thermal resistance of the package,
making the package suitable for high current
applications. The thermal pad is soldered to the top
ground pad and is connected to the internal or bottom
ground plane by several vias. The printed circuit board
(PCB) forms a heat sink and dissipates most of the
Copyright ANPEC Electronics Corp.
11
Rev. A.4 - Feb., 2004
www.anpec.com.tw
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