點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
新竹市科學園區展業一路9號7樓之1
9-7F-1, Prosperity RoadⅠ, Hsin-Chu, Taiwan, R.O.C.
DD312
Tel：886-3-5645656
Fax：886-3-5645626
Power Dissipation
Notice that the power dissipation of a semiconductor chip is limited to its package and ambient
temperature, in which the device requires the maximum output current calculated for given
operating conditions. The maximum allowable power consumption can be calculated by the
following equation:
Tj(junction temperature)(max)(°C)– Ta(ambient temperature)(°C)
Pd(max)(Watt) =
Rth(junction-to-air thermal resistance)(°C/Watt)
The relationship between power dissipation and operating temperature can be refer to the figure
below:
4.0
TO-252
3.5
Tj(max)=125 °C
Rth(TO-252)=30.6 °C/Watt
Rth(SOP8)=60 °C/Watt
3.0
2.5
2.0
1.5
1.0
0.5
0.0
SOP8
0
20
40
60
80
100
120
140
Ambient Temperature Ta(°C)
Based on the Pd(max), the maximum allowable voltage of output terminal can be determined by the
following equation:
HIGH CONSTANT CURRENT LED DRIVER
Version:A.001
Page 8
未經授權而逕予重製、複製、使用或公開本文件，行為人得被追究侵權之相關民刑事責任
Unauthorized reproduction, duplication, use or disclosure of this document will be deemed as infringement.
SITI [ SILICON TOUCH TECHNOLOGY INC. ]
