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參數資料
| 型號： | A8431 |
| 廠商： | Allegro MicroSystems, Inc. |
| 元件分類： | LED驅動器 |
| 英文描述： | White LED Driver Constant Current Step-up Converter |
| 中文描述： | 白光LED驅動恒流升壓轉換器 |
| 文件頁數： | 7/10頁 |
| 文件大?。?/td> | 331K |
| 代理商： | A8431 |
7
26185.301
Worcester, Massachusetts 01615-0036 (508) 853-5000
www.allegromicro.com
115 Northeast Cutoff, Box 15036
Allegro MicroSystems, Inc.
A8431
White LED Driver Constant Current Step-up Converter
Schematic 3. Dimming control with filtered PWM
A843
VIN
SW
EN
GND
FB
Li-ion
2.5 V to
4.2 V
C1
1.0 μF
L1
22 μH
D1
C2
0.22 μF
R1
6.3
V
C
(PMW)
R3
90 k
R2
5 k
Enable
R4
10 k
C3
100 nF
1
1
2
3
5
6
4
OVP
Schematic 4. Soft start operation
A843
VIN
SW
EN
GND
FB
Li-ion
2.5V to
4.2V
C1
1.0 μF
L1
22 μH
D1
C2
0.22 μF
R1
6.3
R3
5 k
R2
1 k
Enable
C3
2.2 nF
1
1
2
3
5
6
4
OVP
PWM Control
. The control voltage, V
C
, also can be
generated by a filtered PWM signal, as shown in schematic
3. In this case, a 0% duty cycle (PWM = 0 V) corresponds
to full brightness and a 100% duty cycle causes the LED
current, I
LOAD
, to go to 0 A.
By applying a PWM signal directly to the EN pin, the A8431
is turned on or off, and I
LOAD
is either full (as defined by
R1) or 0 A. By varying the duty cycle of the PWM signal, the
LED brightness can be controlled from off (0% duty cycle)
to full (100% duty cycle). The PWM frequency should be in
the range from 1 kHz to 10 kHz.
Several other schemes are possible, for example, digitally
switching additional resistors across R1 to increase I
LOAD
.
In this case, R1 would be selected for the minimum desired
brightness.
Start-Up
To provide fast start-up operation, no soft start is
implemented in the control circuit. At power-on, the bypass
capacitor, C1, is discharged, which means that the supply
must provide the in-rush current through the inductor, L1.
This can be reduced by modulating the feedback with a soft-start
circuit as shown in schematic 4. When power is first applied, the
capacitor C3 is discharged and pulls the FB pin high, reducing
the output drive to minimum. As C3 charges, when the bottom
drops below about 0.8 V, the feedback from the sense resistor,
R1, takes over full control of the output current.
Preliminary Data Sheet
Subject to Change Without Notice
December 7, 2004
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相關代理商/技術參數 |
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|---|---|
| A8431EEH-T | 制造商:ALLEGRO 制造商全稱:Allegro MicroSystems 功能描述:White LED Driver Constant Current Step-up Converter |
| A8431EEHTR-T | 功能描述:IC LED DRVR WHITE BCKLGHT 6-MLP RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅動器 系列:- 標準包裝:1 系列:- 恒定電流:- 恒定電壓:- 拓撲:PWM，切換式電容器（充電泵） 輸出數:1 內部驅動器:是 類型 - 主要:背光 類型 - 次要:白色 LED 頻率:642kHz 電源電壓:2.7 V ~ 5.5 V 輸出電壓:5V 安裝類型:表面貼裝 封裝/外殼:10-VFDFN 裸露焊盤 供應商設備封裝:10-VSON 包裝:剪切帶 (CT) 工作溫度:-30°C ~ 85°C 產品目錄頁面:1371 (CN2011-ZH PDF) 其它名稱:BD1603NUV-E2CT |
| A84334-000 | 制造商:TE Connectivity 功能描述:VARISTOR 470VDC 5MM 10% LEADED 制造商:TE Connectivity 功能描述:VARISTOR 470V 400A DISC 5MM |
| A8434 | 制造商:ALLEGRO 制造商全稱:Allegro MicroSystems 功能描述:6-Channel High Efficiency Charge Pump White LED Driver |
| A8434EESTR-T | 功能描述:IC LED DRVR WHITE BCKLGHT 16-MLP RoHS:是 類別:集成電路 (IC) >> PMIC - LED 驅動器 系列:- 標準包裝:60 系列:- 恒定電流:- 恒定電壓:- 拓撲:線性（LDO），PWM，升壓（升壓） 輸出數:8 內部驅動器:是 類型 - 主要:背光 類型 - 次要:RGB，白色 LED 頻率:500kHz ~ 1.5MHz 電源電壓:4.75 V ~ 26 V 輸出電壓:45V 安裝類型:* 封裝/外殼:* 供應商設備封裝:* 包裝:* 工作溫度:-40°C ~ 85°C |
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