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LM3421, LM3421-Q1
LM3423, LM3423-Q1
www.ti.com
LM3421/23
100
k :
10V
R SNS
SNVS574E – JULY 2008 – REVISED MAY 2013
Q2
100 nF
DDRV
Figure 31. Buck Level-Shifted PWM Circuit
V O
LM3421/23
R SNS
DPOL
10V
100
k :
Q2
V CC
Q6
100 pF
10 k :
DDRV
Figure 32. Boost Level-Shifted PWM Circuit
LM3423 ONLY: DPOL, FLT, TIMR, and LRDY
The LM3423 has four additional pins: DPOL, FLT, TIMR, and LRDY. The DPOL pin is simply used to invert the
DDRV polarity . If DPOL is left open, then it is internally pulled high and the polarity is correct for driving a series
N-channel dimFET. If DPOL is pulled low then the polarity is correct for using a series P-channel dimFET in high-
side dimming applications. For a parallel P-channel dimFET, as used in the buck topology, leave DPOL open for
proper polarity.
Among the LM3423's other additional pins are TIMR and FLT which can be used in conjunction with an input
disconnect MosFET switch as shown in Figure 33 to protect the module from various fault conditions.
A fault is detected and an 11.5 μA (typical) current is sourced from the TIMR pin whenever any of the following
conditions exist:
1. LED current is above regulation by more than 30%.
2. OVLO has engaged.
3. Thermal shutdown has engaged.
An external capacitor (C TMR ) from TIMR to AGND programs the fault filter time as follows:
C TMR =
t FLT x 11.5 P A
1.24 V
(33)
When the voltage on the TIMR pin reaches 1.24V, the device is latched off and the N-channel MosFET open
drain FLT pin transitions to a high impedance state. The TIMR pin will be immediately pulled to ground (reset) if
the fault condition is removed at any point during the filter period. Otherwise, if the timer expires, the fault will
remain latched until one of three things occurs:
Copyright ? 2008–2013, Texas Instruments Incorporated
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相关代理商/技术参数
LM3423MHX 制造商:Rochester Electronics LLC 功能描述: 制造商:Texas Instruments 功能描述:
LM3423MHX/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
LM3423Q0 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers
LM3423Q0MH 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers
LM3423Q0MH/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
LM3423Q0MHX 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers
LM3423Q0MHX/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
LM3423Q1 制造商:NSC 制造商全称:National Semiconductor 功能描述:N-Channel Controllers for Constant Current LED Drivers