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| 型号： | LM3423MHBKBSTEV/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 17/67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： | 1A |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 35V |
| 特点： | 可调光 |
| 输入电压： | 4.5 ~ 35 V |
| 已供物品： | 板 |
| 已用 IC / 零件： | LM3423 |
| 其它名称： | LM3423MHBKBSTEV |
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And the right half plane zero ( ω Z1 ) is:
SNVS574E – JULY 2008 – REVISED MAY 2013
Z Z 1 =
r D x D c 2
D x L1
(18)
100
80
? Z1
? P1
135
90
GAIN
60
40
20
0
-20
-40
-60
PHASE
0° Phase Margin
45
0
-45
-90
-135
-180
-225
1e-1
1e1
1e3
1e5
1e7
FREQUENCY (Hz)
Figure 22. Uncompensated Loop Gain Frequency Response
Figure 22 shows the uncompensated loop gain in a worst-case scenario when the RHP zero is below the output
pole. This occurs at high duty cycles when the regulator is trying to boost the output voltage significantly. The
RHP zero adds 20dB/decade of gain while loosing 45°/decade of phase which places the crossover frequency
(when the gain is zero dB) extremely high because the gain only starts falling again due to the high frequency
pole (not modeled or shown in figure). The phase will be below -180° at the crossover frequency which means
there is no phase margin (180° + phase at crossover frequency) causing system instability. Even if the output
pole is below the RHP zero, the phase will still reach -180° before the crossover frequency in most cases yielding
instability.
LM3421/23
I LED
R HSP
HSP
High-Side
Sense Amplifier
C FS
V SNS
R SNS
R HSN
HSN
R FS
sets ? P3
sets ? P2
R CSH
C CMP
CSH
COMP
1.24V
Error Amplifier
To PWM
Comparator
R O
Figure 23. Compensation Circuitry
To mitigate this problem, a compensator should be designed to give adequate phase margin (above 45°) at the
crossover frequency. A simple compensator using a single capacitor at the COMP pin (C CMP ) will add a dominant
pole to the system, which will ensure adequate phase margin if placed low enough. At high duty cycles (as
shown in Figure 22 ), the RHP zero places extreme limits on the achievable bandwidth with this type of
compensation. However, because an LED driver is essentially free of output transients (except catastrophic
failures open or short), the dominant pole approach, even with reduced bandwidth, is usually the best approach.
The dominant compensation pole ( ω P2 ) is determined by C CMP and the output resistance (R O ) of the error
amplifier (typically 5 M ? ):
Copyright ? 2008–2013, Texas Instruments Incorporated
17
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 |
|---|---|
| LM3423MHBSTEVAL | 制造商:Texas Instruments 功能描述:N-Channel Controllers For Constant Current LED Drivers Evaluation Board |
| LM3423MHBSTEVAL/NOPB | 功能描述:BOARD EVAL BOOST FOR 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 |
| 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 |
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