- 您现在的位置：买卖IC网 > PDF目录20990 > LM3421Q1MH/NOPB (National Semiconductor)IC LED DRVR HP CONS CURR 16TSSOP PDF资料下载
参数资料
| 型号： | LM3421Q1MH/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 25/67页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONS CURR 16TSSOP |
| 标准包装： | 92 |
| 系列： | PowerWise® |
| 恒定电流： | 是 |
| 拓扑： | PWM，SEPIC，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 无 |
| 类型 - 主要： | 车载 |
| 类型 - 次要： | 高亮度 LED（HBLED） |
| 频率： | 2MHz |
| 电源电压： | 4.5 V ~ 75 V |
| 输出电压： | 3 V ~ 72 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 供应商设备封装： | 16-TSSOP-EP |
| 包装： | 管件 |
| 工作温度： | -40°C ~ 125°C |
| 产品目录页面： | 1284 (CN2011-ZH PDF) |
| 其它名称： | LM3421Q1MH |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页当前第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页第49页第50页第51页第52页第53页第54页第55页第56页第57页第58页第59页第60页第61页第62页第63页第64页第65页第66页第67页
SNVS574E – JULY 2008 – REVISED MAY 2013
In general, Δ i LED-PP is recommended by manufacturers to be less than 40% of the average LED current (I LED ).
Therefore, for the buck regulator with no output capacitance, Δ i L-PP should also be less than 40% of I LED . For the
boost and buck-boost topologies, Δ i L-PP can be much higher depending on the output capacitance value.
However, Δ i L-PP is suggested to be less than 100% of the average inductor current (I L ) to limit the RMS inductor
current.
L1 is also suggested to have an RMS current rating at least 25% higher than the calculated minimum allowable
RMS inductor current (I L-RMS ).
LED DYNAMIC RESISTANCE
When the load is a string of LEDs, the output load resistance is the LED string dynamic resistance plus R SNS .
LEDs are PN junction diodes, and their dynamic resistance shifts as their forward current changes. Dividing the
forward voltage of a single LED (V LED ) by the forward current (I LED ) leads to an incorrect calculation of the
dynamic resistance of a single LED (r LED ). The result can be 5 to 10 times higher than the true r LED value.
Figure 34. Dynamic Resistance
Obtaining r LED is accomplished by refering to the manufacturer's LED I-V characteristic. It can be calculated as
the slope at the nominal operating point as shown in Figure 34 . For any application with more than 2 series
LEDs, R SNS can be neglected allowing r D to be approximated as the number of LEDs multiplied by r LED .
OUTPUT CAPACITOR
For boost and buck-boost regulators, the output capacitor (C O ) provides energy to the load when the recirculating
diode (D1) is reverse biased during the first switching subinterval. An output capacitor in a buck topology will
simply reduce the LED current ripple ( Δ i LED-PP ) below the inductor current ripple ( Δ i L-PP ). In all cases, C O is sized
to provide a desired Δ i LED-PP . As mentioned in the INDUCTOR section, Δ i LED-PP is recommended by
manufacturers to be less than 40% of the average LED current (I LED-PP ).
C O should be carefully chosen to account for derating due to temperature and operating voltage. It must also
have the necessary RMS current rating. Ceramic capacitors are the best choice due to their high ripple current
rating, long lifetime, and good temperature performance. An X7R dieletric rating is suggested.
INPUT CAPACITORS
The input capacitance (C IN ) provides energy during the discontinuous portions of the switching period. For buck
and buck-boost regulators, C IN provides energy during t ON and during t OFF , the input voltage source charges up
C IN with the average input current (I IN ). For boost regulators, C IN only needs to provide the ripple current due to
the direct connection to the inductor. C IN is selected given the maximum input voltage ripple ( Δ v IN-PP ) which can
be tolerated. Δ v IN-PP is suggested to be less than 10% of the input voltage (V IN ).
An input capacitance at least 100% greater than the calculated C IN value is recommended to account for derating
due to temperature and operating voltage. When PWM dimming, even more capacitance can be helpful to
minimize the large current draw from the input voltage source during the rising transistion of the LED current
waveform.
Copyright ? 2008–2013, Texas Instruments Incorporated
25
Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1
相关PDF资料 |
PDF描述 |
|---|---|
| P51-50-A-T-I12-5V-000-000 | SENS 50PSI 22MM 7/16-20-2B 1-5V |
| P51-15-G-H-MD-4.5OVP-000-000 | SENSOR 15PSI M12-1.5 6G .5-4.5V |
| REC5-483.3SRWZ/H/B/M/SMD | CONV DC/DC 5W 18-72VIN 3.3VOUT |
| P51-75-A-B-MD-20MA-000-000 | SENSOR 75PSI 1/8-27NPT 4-20MA |
| REC3-4812SRW/H2/C/M/SMD-R | CONV DC/DC 3W 36-72VIN 12VOUT |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3421Q1MHX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers |
| LM3421Q1MHX/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 |
| LM3421-SEPICEV/NOPB | 功能描述:电源管理IC开发工具 LM3421-SEPIC EVAL BOARD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| LM3423 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers |
| LM3423_11 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:LM3423 Buck-Boost 2 Layer Evaluation Board evaluation board showcases most features |
发布紧急采购，3分钟左右您将得到回复。