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| 型号： | LM3421MHX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 21/67页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONS CURR 16TSSOP |
| 产品培训模块： | LED Design Solutions |
| 标准包装： | 2,500 |
| 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： | 带卷 (TR) |
| 工作温度： | -40°C ~ 125°C |
| 其它名称： | LM3421MHX |
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SNVS574E – JULY 2008 – REVISED MAY 2013
= 1 . 24V x ¨ ¨ UV 1
R UV 1
V TURN
-
ON
?
§ R + R UV 2 ·
?
? 1
(29)
The hysteresis (V HYS ) is defined as follows:
UVLO only
V HYS = 23 P A x R UV 2
PWM dimming and UVLO
(30)
V HYS = 23 P A x ¨ ¨ R UV 2 + UVH
x ( R UV 1 + R UV 2 ) ·
?
1
§ R
?
R UV 1
?
(31)
When "zero current" shutdown and UVLO are implemented together, the EN pin can be used to escape UVLO.
The nDIM pin will pull-up to V IN when EN is pulled low, therefore if V IN is within the UVLO hysteretic window
when EN is pulled high again, the controller will start-up even though V TURN-ON is not exceeded.
PWM DIMMING
The active low nDIM pin can be driven with a PWM signal which controls the main NFET and the dimming FET
(dimFET). The brightness of the LEDs can be varied by modulating the duty cycle of this signal. LED brightness
is approximately proportional to the PWM signal duty cycle, (i.e. 30% duty cycle ~ 30% LED brightness). This
function can be ignored if PWM dimming is not required by using nDIM solely as a V IN UVLO input as described
in the INPUT UNDER-VOLTAGE LOCKOUT (UVLO) section or by tying it directly to V CC or V IN .
Inverted
V IN
R UV2
R UV1
PWM
D DIM
R UVH
LM3421/23
nDIM
Q DIM
Standard
PWM
Figure 29. PWM Dimming Circuit
1. Connect the dimming MosFET (Q DIM ) with the drain to the nDIM pin and the source to AGND. Apply an
external logic-level PWM signal to the gate of Q DIM .
2. Connect the anode of a Schottky diode (D DIM ) to the nDIM pin. Apply an inverted external logic-level PWM
signal to the cathode of the same diode.
The DDRV pin is a PWM output that follows the nDIM PWM input signal. When the nDIM pin rises, the DDRV pin
rises and the PWM latch reset signal is removed allowing the main MosFET Q1 to turn on at the beginning of the
next clock set pulse. In boost and buck-boost topologies, the DDRV pin is used to control a N-channel MosFET
placed in series with the LED load, while it would control a P-channel MosFET in parallel with the load for a buck
topology.
Copyright ? 2008–2013, Texas Instruments Incorporated
21
Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3421Q0 | 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers |
| LM3421Q0MH | 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers |
| LM3421Q0MH/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 |
| LM3421Q0MHNOPB | 制造商:National Semiconductor 功能描述:LED DRVR 5V/9V/12V/15V/18V/24V 16-Pin TSSOP EP Tube |
| LM3421Q0MHX | 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers |
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