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參數(shù)資料
| 型號： | CAT4238TD-GT3 |
| 英文描述： | High Efficiency 10 LED Boost Converter |
| 中文描述： | 高效率的LED升壓轉(zhuǎn)換器10 |
| 文件頁數(shù)： | 10/14頁 |
| 文件大?。?/td> | 290K |
| 代理商： | CAT4238TD-GT3 |
CAT4238
Doc. No. 5019 Rev. A
10
2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
DIMMING CONTROL
There are several methods available to control the
LED brightness.
PWM signal on the ˉˉˉˉˉ
LED brightness dimming can be done by applying a
PWM signal to the ˉˉˉˉˉ input. The LED current is
repetitively turned on and off, so that the average
current is proportional to the duty cycle. A 100% duty
cycle, with ˉˉˉˉˉ always high, corresponds to the
LEDs at nominal current. Figure 1 shows a 1kHz
signal with a 50% duty cycle applied to the ˉˉˉˉˉ pin.
The recommended PWM frequency range is from
100Hz to 2kHz.
Pin
Figure 1. Switching Waveform
with 1kHz PWM on ˉˉˉˉˉ
Filtered PWM Signal
A filtered PWM signal used as a variable DC voltage
can control the LED current. Figure 2 shows the
PWM control circuitry connected to the CAT4238 FB
pin. The PWM signal has a voltage swing of 0V to
2.5V. The LED current can be dimmed within a range
from 0mA to 20mA. The PWM signal frequency can
vary from very low frequency up to 100kHz.
Figure 2. Circuit for Filtered PWM Signal
A PWM signal at 0V DC, or a 0% duty cycle, results
in a max LED current of about 22mA. A PWM signal
with a 93% duty cycle or more, results in an LED
current of 0mA.
V
FB
= 300mV
15
1k
3.1k
3.73k
0V
25V
0.22μF
C1
R
A
R
B
R
2
i
R1
VIN
CAT4238
FB
SHDN
SW
GND
VIN
PWN
Signal
LED
Current
FILTERED PWM DIMMING [0V to 2.5V]
L
25
20
15
10
5
0
0
10
20
30
40
50
60
70
80
90
100
PWM DUTY CYCLE [%]
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|---|---|
| CAT4238TD-GT3 | 制造商:ON Semiconductor 功能描述:IC LED DRIVER BOOST TSOT-23-5 制造商:ON Semiconductor 功能描述:IC, LED DRIVER, BOOST, TSOT-23-5 |
| CAT4238TDI-G | 制造商:ON Semiconductor 功能描述:IC 10-LED DRIVER LOW NOISE BOOST |
| CAT4240 | 制造商:CATALYST 制造商全稱:Catalyst Semiconductor 功能描述:6 Watt Boost LED Driver |
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