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| 型号： | LM3445M/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 23/40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
t OFF =
Finally:
1
1 V LED
K u V BUCK
f SW
(21)
K u V BUCK
L2 =
V LED 1
f SW x ' i
1 V LED
(22)
Refer to DESIGN EXAMPLE to better understand the design process.
SETTING THE LED CURRENT
The LM3445 constant off-time control loop regulates the peak inductor current (I L2 ). The average inductor current
equals the average LED current (I AVE ). Therefore the average LED current is regulated by regulating the peak
inductor current.
I L2-PK
' i L
I AVE
I L2-MIN
I L2 (t)
t ON
t OFF
t
Figure 28. Inductor Current Waveform in CCM
Knowing the desired average LED current, I AVE and the nominal inductor current ripple, Δ i L , the peak current for
an application running in continuous conduction mode (CCM) is defined as follows:
I L2-PK = I AVE + ' 2 i L
Or, the maximum, or "undimmed", LED current would then be,
I AVE(UNDIM) = I L2-PK(UNDIM) - ' 2 i L
(23)
(24)
This is important to calculate because this peak current multiplied by the sense resistor R3 will determine when
the internal comparator is tripped. The internal comparator turns the control MOSFET off once the peak sensed
voltage reaches 750 mV.
I L-PK(UNDIM) =
750 mV
R3
(25)
Current Limit : Under normal circumstances, the trip voltage on the PWM comparator would be less than or
equal to 750 mV, depending on the amount of dimming. However, if there is a short circuit or an excessive load
on the output, higher than normal switch currents will cause a voltage above 1.27V on the ISNS pin which will
trip the I-LIM comparator. The I-LIM comparator will reset the RS latch, turning off Q2. It will also inhibit the Start
Pulse Generator and the COFF comparator by holding the COFF pin low. A delay circuit will prevent the start of
another cycle for 180 μs.
VALLEY FILL CAPACITORS
Determining voltage rating and capacitance value of the valley-fill capacitors:
The maximum voltage seen by the valley-fill capacitors is:
Copyright ? 2009–2013, Texas Instruments Incorporated
Product Folder Links: LM3445
23
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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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