參數(shù)資料
型號(hào)： LM3405A
廠商： National Semiconductor Corporation
英文描述： 1.6MHz, 1A Constant Current Buck LED Driver with Internal Compensation in Tiny SOT23 Package
中文描述： 1.6MHz的，第1A恒流降壓型LED在微型SOT23封裝和內(nèi)部補(bǔ)償驅(qū)動(dòng)器
文件頁(yè)數(shù)： 9/20頁(yè)
文件大?。?/td> 396K
代理商： LM3405A
LED PWM DIMMING
The LED brightness can be controlled by applying a periodic
pulse signal to the EN/DIM pin and varying its frequency and/
or duty cycle. This so-called PWM dimming method controls
the average light output by pulsing the LED current between
the set value and zero. A logic high level at the EN/DIM pin
turns on the LED current whereas a logic low level turns off
the LED current.
Figure 9
shows a typical LED current wave-
form in PWM dimming mode. As explained in the previous
section, there is approximately a 100μs delay from the EN/
DIM signal going high to fully establishing the LED current as
shown in
Figure 10
. This 100μs delay sets a maximum fre-
quency limit for the driving signal that can be applied to the
EN/DIM pin for PWM dimming.
Figure 11
shows the average
LED current versus duty cycle of PWM dimming signal for
various frequencies. The applicable frequency range to drive
LM3405A for PWM dimming is from 100Hz to 5kHz. The dim-
ming ratio reduces drastically when the applied PWM dim-
ming frequency is greater than 5kHz.
30015266
FIGURE 9. PWM Dimming of LEDs using the EN/DIM Pin
30015267
FIGURE 10. Startup Response to EN/DIM with I
F
= 1A
30015283
FIGURE 11. Average LED Current versus Duty Cycle of
PWM Dimming Signal at EN/DIM Pin
UNDER-VOLTAGE LOCKOUT
Under-voltage lockout (UVLO) prevents the LM3405A from
operating until the input voltage exceeds 2.74V (typical). The
UVLO threshold has approximately 440mV of hysteresis, so
the part will operate until V
drops below 2.3V (typical). Hys-
teresis prevents the part from turning off during power up if
V
IN
is non-monotonic.
CURRENT LIMIT
The LM3405A uses cycle-by-cycle current limit to protect the
internal power switch. During each switching cycle, a current
limit comparator detects if the power switch current exceeds
2.0A (typical), and turns off the switch until the next switching
cycle begins.
OVER-CURRENT PROTECTION
The LM3405A has a built in over-current comparator that
compares the FB pin voltage to a threshold voltage that is
60% higher than the internal reference V
. Once the FB pin
voltage exceeds this threshold level (typically 328mV), the in-
ternal NMOS power switch is turned off, which allows the
feedback voltage to decrease towards regulation. This
threshold provides an upper limit for the LED current. LED
current overshoot is limited to 328mV/R1 by this comparator
during transients.
THERMAL SHUTDOWN
Thermal shutdown limits total power dissipation by turning off
the internal power switch when the IC junction temperature
exceeds 165°C. After thermal shutdown occurs, the power
switch does not turn on until the junction temperature drops
below approximately 150°C.
Design Guide
INDUCTOR (L1)
The Duty Cycle (D) can be approximated quickly using the
ratio of output voltage (V
OUT
) to input voltage (V
IN
):
9
www.national.com
L
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參數(shù)描述
LM3405A_08 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.6MHz, 1A Constant Current Buck LED Driver with Internal Compensation in Tiny SOT23 and eMSOP Package
LM3405AEVAL 功能描述:BOARD EVAL FOR LM3405 RoHS:否 類別:編程器，開(kāi)發(fā)系統(tǒng) >> 評(píng)估板 - LED 驅(qū)動(dòng)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(diǎn):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
LM3405AEVAL/NOPB 功能描述:LED 照明開(kāi)發(fā)工具 LM3405A EVAL BOARD RoHS:否 制造商:Fairchild Semiconductor 產(chǎn)品:Evaluation Kits 用于:FL7732 核心: 電源電壓:120V 系列: 封裝:
LM3405AXMK 制造商:NSC 制造商全稱:National Semiconductor 功能描述:1.6MHz, 1A Constant Current Buck LED Driver with Internal Compensation in Tiny SOT23 and eMSOP Package
LM3405AXMK/NOPB 功能描述:LED照明驅(qū)動(dòng)器 RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N
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