- 您现在的位置：买卖IC网 > Sheet目录337 > LT3478IFE#PBF (Linear Technology)IC LED DRVR HP CONS CURR 16TSSOP
LT3478/LT3478-1
OPERATIO
The LT3478/LT3478-1 are high powered LED drivers with
a 42V, 4.5A internal switch and the ability to drive LEDs
with up to 1050mA for LT3478-1 and up to 105mV/R SENSE
for LT3478.
The LT3478/LT3478-1 work similarly to a conventional
current mode boost converter but use LED current (instead
of output voltage) as feedback for the control loop. The
Block Diagram in Figure 1 shows the major functions of
the LT3478/LT3478-1.
For the part to turn on, the V IN pin must exceed 2.8V and
the ? S ? H ? D ? N pin must exceed 1.4V. The ? S ? H ? D ? N pin threshold
allows programming of an undervoltage lockout (UVLO)
threshold for the system input supply using a simple
resistor divider. A 10μA current ?ows into the ? S ? H ? D ? N pin
before part turn on and is removed after part turn on. This
current hysteresis allows programming of hysteresis for
the UVLO threshold. See “Shutdown Pin and Programming
Undervoltage Lockout” in the Applications Information
Section. For micropower shutdown the ? S ? H ? D ? N pin at 0V
reduces V IN supply current to approximately 3μA.
Each LED driver is a current mode step-up switch-
ing regulator. A regulation point is achieved when the
boosted output voltage V OUT across the output LED(s) is
high enough to create current in the LED(s) equal to the
programmed LED current. A sense resistor connected in
series with the LED(s) provides feedback of LED current
to the converter loop.
The basic loop uses a pulse from an internal oscillator to set
the RS ?ip-?op and turn on the internal power NPN switch
Q1 connected between the switch pin, SW, and ground.
Current increases in the external inductor until switch
current limit is exceeded or until the oscillator reaches
its maximum duty cycle. The switch is then turned off,
causing inductor current to lift the SW pin and turn on an
external Schottky diode connected to the output. Inductor
current ?ows via the Schottky diode charging the output
capacitor. The switch is turned back on at the next reset
the V C voltage controls the peak switch current limit and
hence the inductor current available to the output LED(s).
As with all current mode converters, slope compensation
is added to the control path to ensure stability.
The CTRL1 pin is used to program maximum LED current
via Q2. The CTRL2 pin can be used to program a decrease
in LED current versus temperature for maximum reliability
and utilization of the LED(s). A CTRL2 voltage with negative
temperature coef?cient can be created using an external
resistor divider from V REF with temperature dependant
resistance. Unused CTRL2 is tied to V REF .
For True Color PWM dimming, the LT3478/LT3478-1
provide up to a 3000:1 wide PWM dimming range by al-
lowing the duty cycle of the PWM pin (connected to the
IC and an external N-channel MOSFET in series with the
LED(s)) to be reduced from 100% to as low as 0.033%
for a PWM frequency of 100Hz. Dimming by PWM duty
cycle, allows for constant LED color to be maintained over
the entire dimming range.
For robust operation, the LT3478/LT3478-1 monitor system
performance for any of the following faults : V IN or ? S ? H ? D ? N
pin voltages too low and/or inductor current too high
and/or boosted output voltage too high. On detection of
any of these faults, the LT3478/LT3478-1 stop switching
immediately and a soft-start latch is set discharging the
SS pin (see Timing Diagram for SS pin in Figure 11). All
faults are detected internally and do not require external
components. When all faults no longer exist, an internal
12μA supply charges the SS pin with a timing programmed
using a single external capacitor. A gradual ramp up of SS
pin voltage limits switch current during startup.
For optimum component sizing, duty cycle range and ef-
?ciency the LT3478/LT3478-1 allow for a separate inductor
supply V S and for switching frequency to be programmed
from 200kHz up to 2.25MHz using a resistor from the R T
pin to ground. The advantages of these options are covered
in the Applications Informations section.
cycle of the internal oscillator. During normal operation
34781f
9
发布紧急采购，3分钟左右您将得到回复。
相关PDF资料
LT3486EFE#PBF
IC LED DRVR WHITE BCKLGT 16TSSOP
LT3491EDC#TRMPBF
IC LED DRIVER WHITE BCKLGT 6-DFN
LT3492IFE#TRPBF
IC LED DVR HP CONST CURR 28TSSOP
LT3496IUFD#PBF
IC LED DRVR WHT/RGB BCKLT 28-QFN
LT3497EDDB#TRMPBF
IC LED DRIVR WHITE BCKLGT 10-DFN
LT3498EDDB#TRPBF
IC LED DRVR WT/OLED BCKLGT 12DFN
LT3517HUF#PBF
IC LED DRIVER AUTOMOTIVE 16-QFN
LT3519EMS-2#PBF
IC LED DRVR HP CONST CURR 16MSOP
相关代理商/技术参数
LT3478IFE#TRPBF
功能描述:IC LED DRVR HP CONS CURR 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND
LT3478IFE-1
制造商:LINER 制造商全称:Linear Technology 功能描述:4.5A Monolithic LED Drivers with True Color PWM Dimming
LT3478IFE-1#PBF
功能描述:IC LED DRVR HP CONS CURR 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND
LT3478IFE-1#TRPBF
功能描述:IC LED DRVR HP CONS CURR 16TSSOP RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:6,000 系列:- 恒定电流:- 恒定电压:- 拓扑:开路漏极，PWM 输出数:4 内部驱动器:是 类型 - 主要:LED 闪烁器 类型 - 次要:- 频率:400kHz 电源电压:2.3 V ~ 5.5 V 输出电压:- 安装类型:表面贴装 封装/外壳:8-VFDFN 裸露焊盘 供应商设备封装:8-HVSON 包装:带卷 (TR) 工作温度:-40°C ~ 85°C 其它名称:935286881118PCA9553TK/02-TPCA9553TK/02-T-ND
LT3479
制造商:LINER 制造商全称:Linear Technology 功能描述:700mA Low Noise High Current LED Charge Pump
LT3479EDE
制造商:Linear Technology 功能描述:Conv DC-DC Single Step Up 2.5V to 24V 14-Pin DFN EP
LT3479EDE#PBF
功能描述:IC REG BOOST INV ADJ 3A 14DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2
LT3479EDE#PBF
制造商:Linear Technology 功能描述:DC-DC CONVERTER CURRENT MODE 制造商:Linear Technology 功能描述:DC-DC CONVERTER, CURRENT MODE, 3.5MHZ, D