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| 型号： | LM3445-EDSNEV/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 15/40页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL LED DRIVER LM3445 |
| 标准包装： | 1 |
| 系列： | PowerWise® |
| 电流 - 输出 / 通道： | 205 ~ 340 mA |
| 输出及类型： | 1，非隔离 |
| 特点： | 可调光 |
| 输入电压： | 85 ~ 135 VAC |
| 已供物品： | 板 |
| 已用 IC / 零件： | LM3445 |
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LM3445MM
D10
C12
V BUCK
L2
SNVS570L – JANUARY 2009 – REVISED MAY 2013
R4
Q3
I COLL
GATE
8
Q2
4
COFF
ISNS
7
R3
GND
6
C11
Figure 21. LM3445 Buck Regulation Circuit
OVERVIEW OF CONSTANT OFF-TIME CONTROL
A buck converter’s conversion ratio is defined as:
V IN = D = t ON + t OFF = t ON x f SW
V O t ON
(3)
Constant off-time control architecture operates by simply defining the off-time and allowing the on-time, and
therefore the switching frequency, to vary as either V IN or V O changes. The output voltage is equal to the LED
string voltage (V LED ), and should not change significantly for a given application. The input voltage or V BUCK in
this analysis will vary as the input line varies. The length of the on-time is determined by the sensed inductor
current through a resistor to a voltage reference at a comparator. During the on-time, denoted by t ON , MOSFET
switch Q2 is on causing the inductor current to increase. During the on-time, current flows from V BUCK , through
the LEDs, through L2, Q2, and finally through R3 to ground. At some point in time, the inductor current reaches a
maximum (I L2-PK ) determined by the voltage sensed at R3 and the ISNS pin. This sensed voltage across R3 is
compared against the voltage of dim decoder output, FLTR2, at which point Q2 is turned off by the controller.
Copyright ? 2009–2013, Texas Instruments Incorporated
Product Folder Links: LM3445
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3445EVM-695 | 功能描述:LM3445 1, Non-Isolated Output LED Driver Evaluation Board 制造商:texas instruments 系列:- 零件状态:有效 电流 - 输出/通道:500mA 输出和类型:1，非隔离 电压 - 输出:- 特性:可调光 电压 - 输入:90 ~ 135 VAC 所含物品:板 使用的 IC/零件:LM3445 标准包装:1 |
| LM3445M | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Triac Dimmable Offline LED Driver |
| LM3445M/NOPB | 功能描述:LED照明驱动器 RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N |
| LM3445M/NOPB NOPB | 制造商:Texas Instruments 功能描述:TRIAC DIMMABLE LED DRIVER |
| LM3445MM | 制造商:Texas Instruments 功能描述:LED DRIVER, TRIAC DIMMABLE, 10MSOP |
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