- 您现在的位置：买卖IC网 > PDF目录17193 > LM3423BBLSCSEV/NOPB (National Semiconductor)BOARD EVAL BUCK BOOST LM3423 PDF资料下载
参数资料
| 型号： | LM3423BBLSCSEV/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 22/67页 |
| 文件大小： | 0K |
| 描述： | BOARD EVAL BUCK BOOST LM3423 |
| 标准包装： | 1 |
| 系列： | PowerWise® |
| 电流 - 输出 / 通道： | 700mA |
| 输出及类型： | 1，非隔离 |
| 输入电压： | 10 ~ 70 V |
| 已供物品： | 板，文档 |
| 已用 IC / 零件： | LM3423 |
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页当前第22页第23页第24页第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
The series dimFET will open the LED load, when nDIM is low, effectively speeding up the rise and fall times of
the LED current. Without any dimFET, the rise and fall times are limited by the inductor slew rate and dimming
frequencies above 1 kHz are impractical. Using the series dimFET, dimming frequencies up to 30 kHz are
achievable. With a parallel dimFET (buck topology), even higher dimming frequencies are achievable.
When using the PWM functionality in a boost regulator, the PWM signal can drive a ground referenced FET.
However, with buck-boost and buck topologies, level shifting circuitry is necessary to translate the PWM dim
signal to the floating dimFET as shown in Figure 30 and Figure 31 . If high side dimming is necessary in a boost
regulator using the LM3423, level shifting can be added providing the polarity inverting DPOL pin is pulled low
When using a series dimFET to PWM dim the LED current, more output capacitance is always better. A general
rule of thumb is to use a minimum of 40 μF when PWM dimming. For most applications, this will provide
adequate energy storage at the output when the dimFET turns off and opens the LED load. Then when the
dimFET is turned back on, the capacitance helps source current into the load, improving the LED current rise
time.
A minimum on-time must be maintained in order for PWM dimming to operate in the linear region of its transfer
function. Because the controller is disabled during dimming, the PWM pulse must be long enough such that the
energy intercepted from the input is greater than or equal to the energy being put into the LEDs. For boost and
buck-boost regulators, the minimum dimming pulse length in seconds (t PULSE ) is:
2 x I LED x V O X L1
t PULSE =
V IN 2
(32)
Even maintaining a dimming pulse greater than t PULSE , preserving linearity at low dimming duty cycles is difficult.
The second helpful modification is to remove the C FS capacitor and R FS resistor, eliminating the high frequency
compensation pole. This should not affect stability, but it will speed up the response of the CSH pin, specifically
at the rising edge of the LED current when PWM dimming, thus improving the achievable linearity at low dimming
duty cycles.
LED+
LM3421/23
10 :
5 k :
Q7
100 nF
Q2
V CC
Q6
Q4
R SNS
10V
500 :
100 pF
V IN
DDRV
Figure 30. Buck-boost Level-Shifted PWM Circuit
22
Copyright ? 2008–2013, Texas Instruments Incorporated
Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1
相关PDF资料 |
PDF描述 |
|---|---|
| GCA10DRMI-S288 | CONN EDGECARD 20POS .125 EXTEND |
| ESM06DTKN-S288 | CONN EDGECARD 12POS .156 EXTEND |
| RNM-1509S | CONV DC/DC 1W 15VIN 09VOUT |
| T95Z156K025CZSL | CAP TANT 15UF 25V 10% 2910 |
| ESM06DTKH-S288 | CONN EDGECARD 12POS .156 EXTEND |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3423BS2LYEV/NOPB | 功能描述:LED 照明开发工具 LM3423BS2LY EVAL BOARD 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: |
| LM3423MH | 制造商:Texas Instruments 功能描述:LED DRVR 3Segment 5V/9V/12V/15V/18V/24V 20-Pin TSSOP EP Rail 制造商:Texas Instruments 功能描述:LED DRIVER, HI V, 4.5~75V, POWERWISE |
| LM3423MH/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 |
| LM3423MHBKBSTEV | 制造商:Texas Instruments 功能描述:Development Kits And Tools, The Lm3421/23 Are Versatile High Voltage N-Channel Mosfet Controllers For LED Drivers Evaluation Board |
| LM3423MHBKBSTEV/NOPB | 功能描述:BOARD EVAL BUCK BOOST LM3423 RoHS:是 类别:编程器，开发系统 >> 评估板 - LED 驱动器 系列:PowerWise® 标准包装:1 系列:PowerWise® 电流 - 输出 / 通道:20mA 输出及类型:1，非隔离 输出电压:17V 特点:可调光 输入电压:2.7 ~ 5.5 V 已供物品:板 已用 IC / 零件:LM3508 相关产品:LM3508TLX-ND - IC LED DRVR WHT BCKLGT 9USMDLM3508TLDKR-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLCT-ND - IC LED DRVR WHT BCKLGT 9MICROSMDLM3508TLTR-ND - IC LED DRVR WHT BCKLGT 9MICROSMD |
发布紧急采购，3分钟左右您将得到回复。