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| 型号： | LM3445M/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 22/40页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVER TRIAC DIMM 14SOIC |
| 特色产品： | LM3445 TRIAC Dimmable LED Driver |
| 标准包装： | 55 |
| 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： | 管件 |
| 工作温度： | -40°C ~ 125°C |
| 产品目录页面： | 1285 (CN2011-ZH PDF) |
| 其它名称： | LM3445M |
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SNVS570L – JANUARY 2009 – REVISED MAY 2013
C12
D10
V BUCK
V LED
-
L2
V L2
-
Q2
R3
Figure 27. LM3445 External Components of the Buck Converter
The equation for an ideal inductor is:
Q = L di
dt
(14)
Given a fixed inductor value, L, this equation states that the change in the inductor current over time is
proportional to the voltage applied across the inductor.
During the on-time, the voltage applied across the inductor is,
V L(ON-TIME) = V BUCK - (V LED + V DS(Q2) + I L2 x R3)
(15)
Since the voltage across the MOSFET switch (Q2) is relatively small, as is the voltage across sense resistor R3,
we can simplify this to approximately,
V L(ON-TIME) = V BUCK - V LED
During the off-time, the voltage seen by the inductor is approximately:
V L(OFF-TIME) = V LED
(16)
(17)
The value of V L(OFF-TIME) will be relatively constant, because the LED stack voltage will remain constant. If we
rewrite the equation for an inductor inserting what we know about the circuit during the off-time, we get:
V L(OFF-TIME) = V LED = L x ' ' t i
' i # t OFF x V L2
V L(OFF-TIME) = V LED = L x
Re-arranging this gives:
LED
(I (MAX) - I (MIN) )
' t
(18)
(19)
From this we can see that the ripple current ( Δ i) is proportional to off-time (t OFF ) multiplied by a voltage which is
dominated by V LED divided by a constant (L2).
These equations can be rearranged to calculate the desired value for inductor L2.
L2 # t OFF x ' LED
Where:
V
i
(20)
22
Product Folder Links: LM3445
Copyright ? 2009–2013, Texas Instruments Incorporated
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3445MX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:Triac Dimmable Offline LED Driver |
| LM3445MX/NOPB | 功能描述:板上安装温度传感器 RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| 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 |
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