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| 型号： | LM3421MHX/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 24/67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. The EN pin is pulled low long enough for the V CC pin to drop below 4.1V (approximately 200 ms).
2. The TIMR pin is pulled to ground.
3. A complete power cycle occurs.
When using the EN and OVP pins in conjunction with the RPD pull-down pin, a race condition exists when
exiting the disabled (EN low) state. When disabled, the OVP pin is pulled up to the output voltage because the
RPD pull-down is disabled, and this will appear to be a real OVLO condition. The timer pin will immediately rise
and latch the controller to the fault state. To protect against this behavior, a minimum timer capacitor (C TMR =
220pF) should be used. If fault latching is not required, short the TMR pin to AGND which will disable the FLT
flag function.
The LM3423 also includes an LED Ready (LRDY) flag to notify the system that the LEDs are in proper
regulation. The N-channel MosFET open drain LRDY pin is pulled low whenever any of the following conditions
are met:
1. V CC UVLO has engaged.
2. LED current is below regulation by more than 20%.
3. LED current is above regulation by more than 30%.
4. Over-voltage protection has engaged
5. Thermal shutdown has engaged.
6. A fault has latched the device off.
Note that the LRDY pin is pulled low during startup of the device and remains low until the LED current is in
regulation.
V IN
V SW
LM3421/23
FLT
V IN
High = LED in regulation
LRDY
TIMR
Figure 33. Fault Detection and LED Status Circuit
Design Considerations
This section describes the application level considerations when designing with the LM3421/23. For
corresponding calculations, refer to the Design Guide section.
INDUCTOR
The inductor (L1) is the main energy storage device in a switching regulator. Depending on the topology, energy
is stored in the inductor and transfered to the load in different ways (as an example, buck-boost operation is
detailed in the CURRENT REGULATORS section). The size of the inductor, the voltage across it, and the length
of the switching subinterval (t ON or t OFF ) determines the inductor current ripple ( Δ i L-PP ). In the design process, L1
is chosen to provide a desired Δ i L-PP . For a buck regulator the inductor has a direct connection to the load, which
is good for a current regulator. This requires little to no output capacitance therefore Δ i L-PP is basically equal to
the LED ripple current Δ i LED-PP . However, for boost and buck-boost regulators, there is always an output
capacitor which reduces Δ i LED-PP , therefore the inductor ripple can be larger than in the buck regulator case
where output capacitance is minimal or completely absent.
24
Copyright ? 2008–2013, Texas Instruments Incorporated
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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