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参数资料
| 型号： | LT3587EUD#PBF |
| 厂商： | LINEAR TECHNOLOGY CORP |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING REGULATOR, 1200 kHz SWITCHING FREQ-MAX, PQCC20 |
| 封装： | 3 X 3 MM, LEAD FREE, PLASTIC, QFN-20 |
| 文件页数： | 9/24页 |
| 文件大小： | 395K |
| 代理商： | LT3587EUD#PBF |
LT3587
17
3587fc
APPLICATIONS INFORMATION
Figure 14. PWM Dimming Waveforms
Dimming the LEDs via a PWM signal essentially involves
turning the LEDs on and off at the PWM frequency. The
typical human eye has a sensitivity limit of ~60Hz. By
increasing the PWM frequency to ~80Hz or higher, the eye
will interpret that the pulsed light source is continuously
on. Additionally, by modulating the duty cycle (amount of
“on-time”), intensity of the LEDs is controlled. The color
of the LEDs remains unchanged in this scheme since the
LED current is either zero or a constant value.
Figure 13 shows a partial application showing an LED
driver for six white LEDs. If the voltage at the CAP3 pin is
higher than 10V when the LEDs are on, direct PWM dim-
ming method requires an external NMOS. This external
NMOS is tied between the cathode of the lowest LED in
the string and ground as shown in Figure 13.
A Si1304 logic-level MOSFET can be used since its source
is connected to ground, and it is able to withstand the
open-circuit voltage at the VOUT3 pin across its drain and
source. The PWM signal must be applied to the EN/SS3
pin of the LT3587 and the gate of the NMOS. The PWM
signal should traverse between 0V to 2.5V, to ensure
proper turn on and off of the Boost3 regulation loop and
the NMOS transistor MN1. When the PWM signal goes
high, the LEDs are connected to ground and a current of
IVOUT3 = 160V/RIFB3 ows through the LEDs. When the
PWM signal goes low, the LEDs are disconnected and
turned off.
The output disconnect feature and the external NMOS
ensure that the LEDs quickly turn off without discharging
the output capacitor. This allows the LEDs to turn on faster.
Figure 14 shows the PWM dimming waveforms for the
circuit in Figure 13.
Figure 13. Six White LEDs Driver With PWM Dimming
10μH
3587 F13
VOUT3
CAP3
IFB3
LT3587
RIFB3
8.06k
EN/SS3
SW3
VIN
LED DRIVER
20mA
1μF
VVIN
2.5V TO 5V
PWM
FREQ
2.5V
0V
MN1
Si1304BDL
3587 F14
ENSS3
5V/DIV
IL4
200mA/DIV
IVOUT3
13mA/DIV
2ms/DIV
VVIN = 3.6V
6 LEDs
0mA
0V
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LT3587EUD-TRPBF | 制造商:LINER 制造商全称:Linear Technology 功能描述:High Voltage Monolithic Inverter and Dual Boost |
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| LT3590EDC#PBF | 制造商:Linear Technology 功能描述:IC LED DRIVER BULK MODE 48V 制造商:Linear Technology 功能描述:IC, LED DRIVER, BULK MODE, 48V |
| LT3590EDC#TRMPBF | 功能描述:IC LED DRIVER WHITE BCKLGT 6-DFN 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 |
| LT3590EDC#TRPBF | 功能描述:IC LED DRIVER WHITE BCKLGT 6-DFN 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 |
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