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參數(shù)資料
| 型號： | LM3402 |
| 廠商： | National Semiconductor Corporation |
| 英文描述： | 0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| 中文描述： | 0.5A的恒流降壓穩(wěn)壓器用于驅(qū)動高功率LED |
| 文件頁數(shù)： | 20/22頁 |
| 文件大小： | 840K |
| 代理商： | LM3402 |
Layout Considerations
(Continued)
The dark grey, inner loop represents the high current path
during the MOSFET on-time. The light grey, outer loop rep-
resents the high current path during the off-time.
GROUND PLANE AND SHAPE ROUTING
The diagram of Figure 6 is also useful for analyzing the flow
of continuous current vs. the flow of pulsating currents. The
circuit paths with current flow during both the on-time and
off-time are considered to be continuous current, while those
that carry current during the on-time or off-time only are
pulsating currents. Preference in routing should be given to
the pulsating current paths, as these are the portions of the
circuit most likely to emit EMI. The ground plane of a PCB is
a conductor and return path, and it is susceptible to noise
injection just as any other circuit path. The continuous cur-
rent paths on the ground net can be routed on the system
ground plane with less risk of injecting noise into other
circuits. The path between the input source and the input
capacitor and the path between the recirculating diode and
the LEDs/current sense resistor are examples of continuous
current paths. In contrast, the path between the recirculating
diode and the input capacitor carries a large pulsating cur-
rent. This path should be routed with a short, thick shape,
preferably on the component side of the PCB. Multiple vias
in parallel should be used right at the pad of the input
capacitor to connect the component side shapes to the
ground plane. A second pulsating current loop that is often
ignored is the gate drive loop formed by the SW and BOOT
pins and capacitor CB. To minimize this loop at the EMI it
generates, keep CB close to the SW and BOOT pins.
CURRENT SENSING
The CS pin is a high-impedance input, and the loop created
by R
, R
(if used), the CS pin and ground should be
made as small as possible to maximize noise rejection. R
should therefore be placed as close as possible to the CS
and GND pins of the IC.
REMOTE LED ARRAYS
In some applications the LED or LED array can be far away
(several inches or more) from the LM3402/02HV, or on a
separate PCB connected by a wiring harness. When an
output capacitor is used and the LED array is large or
separated from the rest of the converter, the output capacitor
should be placed close to the LEDs to reduce the effects of
parasitic inductance on the AC impedance of the capacitor.
The current sense resistor should remain on the same PCB,
close to the LM3402/02HV.
20192128
FIGURE 6. Buck Converter Current Loops
L
www.national.com
20
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| LM3402_07 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| LM3402_08 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:0.5A Constant Current Buck Regulator for Driving High Power LEDs |
| LM3402_1 | 制造商:NSC 制造商全稱:National Semiconductor 功能描述:LM3402/LM3404 Fast Dimming and True Constant LED Current Evaluation Board |
| LM3402EVAL | 功能描述:BOARD EVALUATION FOR LM3402 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 評估板 - LED 驅(qū)動器 系列:PowerWise® 標(biāo)準(zhǔn)包裝:1 系列:PowerWise® 電流 - 輸出 / 通道:20mA 輸出及類型:1，非隔離 輸出電壓:17V 特點:可調(diào)光 輸入電壓:2.7 ~ 5.5 V 已供物品:板 已用 IC / 零件:LM3508 相關(guān)產(chǎn)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 |
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