- 您现在的位置：买卖IC网 > PDF目录17193 > LM3423BBLSCSEV/NOPB (National Semiconductor)BOARD EVAL BUCK BOOST LM3423 PDF资料下载
参数资料
| 型号： | LM3423BBLSCSEV/NOPB |
| 厂商： | National Semiconductor |
| 文件页数： | 19/67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 |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页当前第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页第37页第38页第39页第40页第41页第42页第43页第44页第45页第46页第47页第48页第49页第50页第51页第52页第53页第54页第55页第56页第57页第58页第59页第60页第61页第62页第63页第64页第65页第66页第67页
SNVS574E – JULY 2008 – REVISED MAY 2013
START-UP REGULATOR
The LM3421/23 includes a high voltage, low dropout bias regulator. When power is applied, the regulator is
enabled and sources current into an external capacitor (C BYP ) connected to the V CC pin. The recommended
bypass capacitance for the V CC regulator is 2.2 μF to 3.3 μF. The output of the V CC regulator is monitored by an
internal UVLO circuit that protects the device from attempting to operate with insufficient supply voltage and the
supply is also internally current limited. Figure 25 shows the typical start-up waveforms for the LM3421/23.
First, C BYP is charged to be above V CC UVLO threshold (~4.2V). The C VCC charging time (t VCC ) can be estimated
as:
t VCC =
4 . 2 V
25 mA
x C BYP = 168 : x C BYP
(22)
C CMP is then charged to 0.9V over the charging time (t CMP ) which can be estimated as:
t CMP =
0.9V
25 P A
x C CMP = 36 k : x C CMP
(23)
Once C CMP = 0.9V, the part starts switching to charge C O until the LED current is in regulation. The C O charging
time (t CO ) can be roughly estimated as:
t CO = C O x
V O
I LED
(24)
The system start-up time (t SU ) is defined as:
t SU = t VCC + t CMP + t CO
(25)
In some configurations, the start-up waveform will overshoot the steady state COMP pin voltage. In this case, the
LED current and output voltage will overshoot also, which can trip the over-voltage or protection, causing a race
condition. The easiest way to prevent this is to use a larger compensation capacitor (C CMP ), thereby slowing
down the control loop.
OVER-VOLTAGE LOCKOUT (OVLO)
V O
LM3421/23
23 P A
R OV2
OVP
1.24V
OVLO
R OV1
Figure 26. Over-Voltage Protection Circuitry
The LM3421/23 can be configured to detect an output (or input) over-voltage condition via the OVP pin. The pin
features a precision 1.24V threshold with 23 μA (typical) of hysteresis current as shown in Figure 26 . When the
OVLO threshold is exceeded, the GATE pin is immediately pulled low and a 23 μA current source provides
hysteresis to the lower threshold of the OVLO hysteretic band.
If the LEDs are referenced to a potential other than ground (floating), as in the buck-boost and buck
configuration, the output voltage (V O ) should be sensed and translated to ground by using a single PNP as
The over-voltage turn-off threshold (V TURN-OFF ) is defined:
Ground Referenced
V TURN - OFF = 1 . 24V x ¨ ¨ OV 1
§ R + R OV 2 ·
?
? R OV 1 1
?
(26)
Copyright ? 2008–2013, Texas Instruments Incorporated
19
Product Folder Links: LM3421 LM3421-Q1 LM3423 LM3423-Q1
相关PDF资料 |
PDF描述 |
|---|---|
| GCA10DRMI-S288 | CONN EDGECARD 20POS .125 EXTEND |
| ESM06DTKN-S288 | CONN EDGECARD 12POS .156 EXTEND |
| RNM-1509S | CONV DC/DC 1W 15VIN 09VOUT |
| T95Z156K025CZSL | CAP TANT 15UF 25V 10% 2910 |
| ESM06DTKH-S288 | CONN EDGECARD 12POS .156 EXTEND |
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 |
发布紧急采购，3分钟左右您将得到回复。