RT8079GQW 查看數據表（PDF） - Richtek Technology
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RT8079GQW Datasheet PDF : 13 Pages
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RT8079
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
WQFN-16L 3x3 package, the thermal resistance, θJA, is
47°C/W on a standard JEDEC 51-7 four-layer thermal test
board. The maximum power dissipation at TA = 25°C can
be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (47°C/W) = 2.128W for
WQFN-16L 3x3 package
The maximum power dissipation depends on the operating
ambient temperature for fixed TJ(MAX) and thermal
resistance, θJA. The derating curve in Figure 2 allows the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
2.4
Four-Layer PCB
2.0
1.6
1.2
0.8
0.4
0.0
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 2. Derating Curve of Maximum Power Dissipation
Layout Considerations
For the best performance of the RT8079, the following
guidelines must be strictly followed.
` The input capacitor should be placed as close as possible
to the device pins (VIN and GND).
` The RT/SYNC pin is sensitive. The RT resistor should
be located as close as possible to the IC and minimal
lengths of trace.
` The SW node is with high frequency voltage swing. It
should be kept at a small area.
` Place the feedback components as close as possible
to the IC and keep away from the noisy devices.
` The GND and AGND should be connected to a strong
ground plane for heat sinking and noise protection.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8079-01 February 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
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