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| 型号： | LM3423BBLSCSEV/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 16/67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 |
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SNVS574E – JULY 2008 – REVISED MAY 2013
OVER-CURRENT PROTECTION
The LM3421/23 devices have a secondary method of over-current protection. Switching action is disabled
whenever the current in the LEDs is more than 30% above the regulation set point. The dimming MosFET switch
driver (DDRV) is not disabled however as this would immediately remove the fault condition and cause oscillatory
behavior.
ZERO CURRENT SHUTDOWN
The LM3421/23 devices implement "zero current" shutdown via the EN and RPD pins. When pulled low, the EN
pin places the devices into near-zero current state, where only the leakage currents will be observed at the pins
(typical 0.1 μA). The applications circuits, frequently have resistor dividers to set UVLO, OVLO, or other similar
functions. The RPD pin is an open drain N-channel MosFET that is enabled only when the device is enabled.
Tying the bottom of all resistor dividers to the RPD pin as shown in Figure 21 allows them to float during
shutdown, thus removing their current paths and providing true application-wide zero current shutdown.
V IN
L1
D1
V O
Enable
LM3421/23
R UV2
EN
V IN
nDIM
OVP
RPD
R OV2
R OV1
R UV1
Figure 21. Zero Current Shutdown Circuit
CONTROL LOOP COMPENSATION
The LM3421/23 control loop is modeled like any current mode controller. Using a first order approximation, the
uncompensated loop can be modeled as a single pole created by the output capacitor and, in the boost and
buck-boost topologies, a right half plane zero created by the inductor, where both have a dependence on the
LED string dynamic resistance. There is also a high frequency pole in the model, however it is near the switching
frequency and plays no part in the compensation design process therefore it will be neglected. Since ceramic
capacitance is recommended for use with LED drivers due to long lifetimes and high ripple current rating, the
ESR of the output capacitor can also be neglected in the loop analysis. Finally, there is a DC gain of the
uncompensated loop which is dependent on internal controller gains and the external sensing network.
A buck-boost regulator will be used as an example case. See the Design Guide section for compensation of all
topologies.
The uncompensated loop gain for a buck-boost regulator is given by the following equation:
¨ 1 -
¨ 1 +
s ·
Z Z 1 ?
s ·
Z P 1 ?
T U = T U 0 x
§
¨
?
§
¨
?
?
1
?
1
(15)
Where the uncompensated DC loop gain of the system is described as:
T U 0 =
D c x 500V x R CSH x R SNS
( 1 + D ) x R HSP x R LIM
=
D c x 620V
( 1 + D ) x I LED x R LIM
(16)
3
Z P 1 =
And the output pole ( ω P1 ) is approximated:
1+ D
r D x C O
(17)
16
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 |
|---|---|
| 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 |
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