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| 型号： | LT3478IFE-1#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 12/24页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR HP CONS CURR 16TSSOP |
| 标准包装： | 95 |
| 恒定电流： | 是 |
| 拓扑： | PWM，降压（降压），升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 车载，背光 |
| 类型 - 次要： | 颜色，白色 LED |
| 频率： | 200kHz ~ 2.25MHz |
| 电源电压： | 2.8 V ~ 36 V |
| 输出电压： | 42V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-TSSOP（0.173"，4.40mm）裸露焊盘 |
| 供应商设备封装： | 16-TSSOP-EP |
| 包装： | 管件 |
| 工作温度： | -40°C ~ 125°C |
| 产品目录页面： | 1339 (CN2011-ZH PDF) |
LT3478/LT3478-1
APPLICATIO S I FOR ATIO
Programming Maximum LED current
Maximum LED current can be programmed using the CTRL1
pin with CTRL2 tied to the V REF pin (see Figures 4 and 5).
The maximum allowed LED current is de?ned as:
(LT3478-1) Max LED Current = Min(CTRL1, 1.05) Amps
( LT 3478 ) Max LED Current =
maximum allowed LED current versus temperature to
warn against exceeding this current limit and damaging
the LED (Figure 6).
Luxeon V (Maximum) and LT3478-1
(Programmed) Current Derating
Curves vs Temperature
900
Min ( CTRL 1 , 1 . 05 ) ?
0 . 1
R S E NSE
Amps
800
700
600
LUXEON V EMITTER
CURRENT DERATING
CURVE
LED current vs CTRL1 is linear for approximately
500
400
EXAMPLE
0.1V < CTRL1 < 0.95V
For maximum possible LED current, connect CTRL1 and
CTRL2 to the V REF pin.
300
200
100
0
LT3478-1
PROGRAMMED LED
CURRENT DERATING CURVE
1400
T A = 25 ° C
CTRL2 = V REF
0
25 50 75
T A AMBIENT TEMPERATURE ( ° C)
100
1050
(FOR LT3478 SCALE
BY 0.1 ? /R SENSE )
LUXEON V EMITTER
(GREEN, CYAN, BLUE, ROYAL BLUE)
θ JA = 20 ° C/W
3478 F06
700
LT3478-1
Figure 6. LED Current Derating Curve vs Ambient Temperature
Without the ability to back off LED current as temperature
350
V REF
increases, many LED drivers are limited to driving the
LED(s) at only 50% or less of their maximum rated currents.
0
0
0.35
0.70
CTRL1 (V)
1.05
1.40
3478 F04
This limitation requires more LEDs to obtain the intended
brightness for the application. The LT3478/LT3478-1 al-
low the output LED(s) to be programmed for maximum
Figure 4. LED Current vs CTRL1 Voltage
allowable current while still protecting the LED(s) from
excessive currents at high temperature. This is achieved
R2
R1
10
13
12
LT3478/LT3478-1
V REF V OUT
CTRL2
CTRL1 LED
3478 F05
(LT3478)
R SENSE
by programming a voltage at the CTRL2 pin with a nega-
tive temperature coef?cient using a resistor divider with
temperature dependent resistance (Figures 7 and 8).
CTRL2 voltage is programmed higher than CTRL1 voltage.
This allows initial LED current to be de?ned by CTRL1.
As temperature increases, CTRL2 voltage will fall below
CTRL1 voltage causing LED currents to be controlled by
Figure 5. Programming LED Current
Programming LED Current Derating vs Temperature
A useful feature of the LT3478/LT3478-1 is the ability
to program a derating curve for maximum LED current
versus temperature. LED data sheets provide curves of
CTRL2 pin voltage. The choice of resistor ratios and use
of temperature dependent resistance in the divider for the
CTRL2 pin will de?ne the LED current curve breakpoint
and slope versus temperature (Figure 8).
A variety of resistor networks and NTC resistors with differ-
ent temperature coef?cients can be used for programming
34781f
12
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相关代理商/技术参数 |
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|---|---|
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| 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 |
| LT3479EDE#TRPBF | 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:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
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