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參數(shù)資料
| 型號(hào)： | LM3401MM |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 顯示驅(qū)動(dòng)器 |
| 英文描述： | ProcessorPM Development Kit |
| 中文描述： | LED DISPLAY DRIVER, PDSO8 |
| 封裝： | PLASTIC, MSOP-8 |
| 文件頁數(shù)： | 6/18頁 |
| 文件大?。?/td> | 324K |
| 代理商： | LM3401MM |
Block Diagram
30021415
FIGURE 1. Block Diagram
Operational Description
HYSTERETIC CONTROL
The LM3401 is a step-down DC-DC controller designed to
provide a constant current source for driving a high power
LED string.
The LM3401 uses comparator-based voltage mode hysteretic
control for a simple and stable design. Hysteretic control does
not utilize an internal oscillator, but relies on output conditions
to directly control switching. The LM3401 controls LED cur-
rent within the adjustable hysteresis window by monitoring
peak and valley voltage at the SNS pin. A dual sided hystere-
sis window is used to optimize accuracy.
Regulated LED current flows to ground through a sense re-
sistor at the SNS pin. The voltage generated at the SNS pin
is compared to the 200 mV internal reference. When the SNS
voltage falls below the reference voltage minus hysteresis,
the output of the hysteretic comparator goes low. This results
in the driver output, HG, pulling the gate of the PFET low and
turning on the PFET.
With the PFET on, LED current ramps up through the PFET
and the inductor. As the LED current increases, the SNS volt-
age reaches its upper threshold (reference voltage plus hys-
teresis). This forces the output of the comparator and HG to
go high, which turns the PFET off. When the PFET turns off,
current flows through the catch diode, and LED and inductor
current ramp down. When the SNS voltage falls to its lower
threshold, the cycle repeats. The resulting LED current, SNS,
and switch node waveforms are shown in
Figure 2
.
30021416
FIGURE 2. Hysteretic Switching Waveforms
OUTPUT CURRENT SETTING
The LED average current is programmed using a resistor be-
tween SNS and GND, shown as R1 in the typical application
schematic. The SNS resistor (R
SNS
) can be calculated as fol-
lows:
Where V
is 200 mV typically, and I
LED
is the DC average
LED current.
The sense resistor power rating must be higher than its power
dissipation. The required power rating can be calculated (in
Watts) as follows:
www.national.com
6
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3401MM/NOPB | 功能描述:LED照明驅(qū)動(dòng)器 HYSTERETIC PFET CONTROLLER RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| LM3401MMX | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Hysteretic PFET Controller for High Power LED Drive |
| LM3401MMX/NOPB | 功能描述:LED照明驅(qū)動(dòng)器 RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
| LM3401MMX/S7002590 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述: |
| LM3401-MR16DEMO/NOPB | 功能描述:LED 照明開發(fā)工具 LM3401-MR16DEMO RoHS:否 制造商:Fairchild Semiconductor 產(chǎn)品:Evaluation Kits 用于:FL7732 核心: 電源電壓:120V 系列: 封裝: |
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