DD311_1 Datasheet, PDF (12/20 Pages) Silicon Touch Technology Inc. – HIGH CONSTANT CURRENT LED DRIVER

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.
Tel：886-3-5645656 Fax：886-3-5645626
Power Dissipation
DD311
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:
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
Tj(max)=125 °C
Rth=23.38 °C/Watt
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 calculated as
follows:
Pd(max)(Watt)– VREXT(Volt) × IREF(A)
Vout(max)(Volt) =
Iout(A) × Dimming Duty
HIGH CONSTANT CURRENT LED DRIVER
Version:A.002
Page 11