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参数资料
| 型号： | LM3402_07 |
| 厂商： | National Semiconductor Corporation |
| 英文描述： | 0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| 中文描述： | 0.5A的恒流降压稳压器用于驱动高功率LED |
| 文件页数： | 3/24页 |
| 文件大小： | 431K |
| 代理商： | LM3402_07 |
20192105
FIGURE 1. Comparator and One-Shot
The LM3402/02HV regulators should be operated in contin-
uous conduction mode (CCM), where inductor current stays
positive throughout the switching cycle. During steady-state
operationin the CCM, the converter maintains a constant
switching frequency, which can be selected using the follow-
ing equation:
V
F = forward voltage of each LED, n = number of LEDs in
series
AVERAGE LED CURRENT ACCURACY
The COT architecture regulates the valley of
ΔV
SNS, the AC
portion of V
SNS. To determine the average LED current (which
is also the average inductor current) the valley inductor cur-
rent is calculated using the following expression:
In this equation t
SNS represents the propagation delay of the
CS comparator, and is approximately 220 ns. The average
inductor/LED current is equal to I
L-MIN plus one-half of the in-
ductor current ripple,
Δi
L:
I
F = IL = IL-MIN + ΔiL / 2
Detailed information for the calculation of
Δi
L is given in the
Design Considerations section.
MAXIMUM OUTPUT VOLTAGE
The 300 ns minimum off-time limits on the maximum duty cy-
cle of the converter, D
MAX, and in turn ,the maximum output
voltage V
O(MAX) is determined by the following equations:
The maximum number of LEDs, n
MAX, that can be placed in
a single series string is governed by V
O(MAX) and the maxi-
mum forward voltage of the LEDs used, V
F(MAX), using the
expression:
At low switching frequency the maximum duty cycle and out-
put voltage are higher, allowing the LM3402/02HV to regulate
output voltages that are nearly equal to input voltage. The
following equation relates switching frequency to maximum
output voltage.
MINIMUM OUTPUT VOLTAGE
The minimum recommended on-time for the LM3402/02HV is
300 ns. This lower limit for t
ON determines the minimum duty
cycle and output voltage that can be regulated based on input
voltage and switching frequency. The relationship is deter-
mined by the following equation:
11
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LM3402/LM3402HV
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LM3402EVAL | 功能描述:BOARD EVALUATION FOR LM3402 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 |
| LM3402EVAL | 制造商:Texas Instruments 功能描述:EVAL BOARD |
| LM3402EVAL/NOPB | 功能描述:电源管理IC开发工具 LM3402 EVAL BOARD RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| LM3402HV | 制造商:Texas Instruments 功能描述:Buck Regulator ,0.5A ,LED Drivers,MSOP8 |
| LM3402HVEVAL | 功能描述:BOARD EVALUATION FOR LM3402HV RoHS:是 类别:编程器，开发系统 >> 评估板 - LED 驱动器 系列:PowerSmart® 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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