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| 型号： | LM3445MX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 15/40页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVER TRIAC DIMM 14SOIC |
| 标准包装： | 2,500 |
| 系列： | PowerWise® |
| 恒定电流： | 是 |
| 拓扑： | PWM，降压（降压） |
| 输出数： | 1 |
| 内部驱动器： | 无 |
| 类型 - 次要： | 高亮度 LED（HBLED） |
| 频率： | 30kHz ~ 1MHz |
| 电源电压： | 8 V ~ 12 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 14-SOIC（0.154"，3.90mm 宽） |
| 供应商设备封装： | 14-SOICN |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 125°C |
| 其它名称： | LM3445MX |
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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
15
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相关代理商/技术参数 |
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|---|---|
| LM3445TRIACEVAL | 功能描述:BOARD EVAL LM3445MM RoHS:否 类别:编程器，开发系统 >> 过时/停产零件编号 系列:PowerWise® 标准包装:1 系列:- 传感器类型:CMOS 成像，彩色（RGB） 传感范围:WVGA 接口:I²C 灵敏度:60 fps 电源电压:5.7 V ~ 6.3 V 嵌入式:否 已供物品:成像器板 已用 IC / 零件:KAC-00401 相关产品:4H2099-ND - SENSOR IMAGE WVGA COLOR 48-PQFP4H2094-ND - SENSOR IMAGE WVGA MONO 48-PQFP |
| LM3445TRIACEVAL/NOPB | 制造商:Texas Instruments 功能描述:TRIAC Dimmable Offline LED Driver Evaluation Board |
| LM3447 | 制造商:TI 制造商全称:Texas Instruments 功能描述:Phase Dimmable, Primary Side Power Regulated PFC Flyback Controller for LED Lighting |
| LM3447-A19-120VEVM | 功能描述:LED 照明开发工具 LM3447 Eval Mod RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
| LM3447-A19-230VEVM | 功能描述:LED 照明开发工具 LM3447 Eval Mod RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装: |
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