- 您现在的位置：买卖IC网 > Datasheet目录356 > SC4540ULTRT (Semtech)IC LED DRIVR CONST CURRENT 8MLPD Datasheet资料下载
参数资料
| 型号： | SC4540ULTRT |
| 厂商： | Semtech |
| 文件页数： | 10/15页 |
| 文件大小： | 0K |
| 描述： | IC LED DRIVR CONST CURRENT 8MLPD |
| 标准包装： | 1 |
| 恒定电流： | 是 |
| 拓扑： | PWM，升压（升压） |
| 输出数： | 1 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 680kHz ~ 920kHz |
| 电源电压： | 2.8 V ~ 12 V |
| 输出电压： | 5 V ~ 38 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 8-UFQFN 裸露焊盘 |
| 供应商设备封装： | 8-UMLP |
| 包装： | 标准包装 |
| 工作温度： | -40°C ~ 85°C |
| 其它名称： | SC4540ULTRTDKR |
SC4540
Applications Information
General Description
The SC4540 contains an 800kHz fixed-frequency current-
mode boost converter and an independent LED current
regulator. The LED current set point is chosen using an
external resistor, while the PWM controller operates inde-
pendently to keep the current in regulation. The SC4540
receives information from the internal LED current regula-
tor and drives the output to the proper voltage with no
user intervention.
The current flowing through the LED string is indepen-
dently controlled by an internal current regulator, unlike
the ballasting resistor methodology that many LED current
regulators use. The internal current regulator can be shut
off entirely without leaking current from a charged output
capacitor or causing false-lighting with low LED count and
high V IN . The backlight current (I BL ) is programmed using
cycle PWM signal used for a few milliseconds provides the
additional advantage of reduced in-rush at start up.
The start-up delay time between the enable signal going
high and the activation of the internal current regulator
causes nonlinearity between the I BL current and the duty
cycle of the PWM frequency seen by the EN pin. As the
PWM signal frequency increases, the total on time per
cycle of the PWM signal decreases. Since the start up delay
time remains constant, the effect of the delay becomes
more noticeable, causing the average I BL to be less predict-
able at lower duty cycles. Recommended minimum duty
cycles are 20% for 50kHz PWM frequency, 10% for 32kHz
PWM frequency and 1% for 200Hz PWM frequency. Refer
to the Normalized I OUT versus Duty Cycle in the Typical
Characteristics section for PWM performance across duty
cycle for different PWM frequencies.
an external resistor.
Zero Duty Cycle Mode
The path from the EN pin to the output control is a high
bandwidth control loop. This feature allows the PWM
dimming frequency to range between 100Hz and 50kHz.
In shutdown mode, leakage through the current regulator
output is less than 1μA. This keeps the output capacitor
charged and ready for instant activation of the LED
Zero duty cycle mode is activated when the voltage on
the BL pin exceeds 1.3V. In this mode, the COMP pin
voltage is pulled low, suspending all switching. This allows
the V OUT and V BL voltages to fall. The COMP voltage is held
low until the V BL falls below 1V, allowing V COMP to return to
its normal operating voltage and switching to resume.
string.
Protection Features
The 800kHz switching speed provides high output power
while allowing the use of a low profile inductor, maximiz-
ing efficiency for space constrained and cost-sensitive
The SC4540 provides several protection features to safe-
guard the device from catastrophic failures. These features
include:
applications. The converter and output capacitor are pro-
tected from open-LED conditions by over-voltage
protection.
PWM Dimming
The enable pin can be toggled to allow PWM dimming. In
?
?
?
?
Over-voltage Protection (OVP)
Soft-start
Thermal Shutdown
Current Limit
a typical application, a microcontroller sets a register or
counter that varies the pulse width on a GPIO pin. The
SC4540 provides dimming between 100Hz and 50kHz.
The SC4540 is compatible with a wide range of devices by
using dimming technology that avoids the audio band by
using high frequency PWM dimming. A wide range of
illumination can be generated while keeping the instanta-
neous LED current at its peak value for luminescent
effi ciency and color purity. The SC4540 can accommodate
any PWM duty cycle between 0 and 100%. A low duty
Over-Voltage Protection (OVP)
A built-in over-voltage protection circuit prevents damage
to the IC and output capacitor in the event of an open-
circuit condition. The output voltage of the boost
converter is detected at the OUT pin and divided inter-
nally. If the voltage at the OUT pin exceeds the OVP limit,
the boost converter is shut down and a pull down is
applied to the OUT pin to quickly discharge the output
capacitor. This additional level of protection prevents a
condition where the output capacitor and Schottky diode
10
相关PDF资料 |
PDF描述 |
|---|---|
| SC4541SKTRT | IC LED DRVR BACKLIGHT SOT23-6 |
| SC5010ULTRT | IC LED DRVR BACKLIGHT I2C 28QFN |
| SC600BIMLTRT | IC LED DRIVR WHITE BCKLGT 10-MLP |
| SC618ULTRT | IC LED DRIVER PHOTO FLASH 10-MLP |
| SC620ULTRT | IC LED DRIVER LINEAR 16-MLPQ |
相关代理商/技术参数 |
参数描述 |
|---|---|
| SC4541SKTRT | 功能描述:IC LED DRVR BACKLIGHT SOT23-6 RoHS:是 类别:集成电路 (IC) >> PMIC - LED 驱动器 系列:- 标准包装:60 系列:- 恒定电流:- 恒定电压:- 拓扑:线性（LDO），PWM，升压（升压） 输出数:8 内部驱动器:是 类型 - 主要:背光 类型 - 次要:RGB，白色 LED 频率:500kHz ~ 1.5MHz 电源电压:4.75 V ~ 26 V 输出电压:45V 安装类型:* 封装/外壳:* 供应商设备封装:* 包装:* 工作温度:-40°C ~ 85°C |
| SC4541ULTRT | 制造商:Semtech Corporation 功能描述:SINGLE WIRE BACKLIGHT DRIVER |
| SC454MLTRT | 制造商:Semtech Corporation 功能描述:PWM Controller 32-Pin MLP T/R 制造商:Semtech Corporation 功能描述:SINGLE PHASE PWR SUPPLY CONTLR |
| SC4560 | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:相机闪光灯控制IC |
| SC457 | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Single-Phase Single Chip Vcore Power Supply |
发布紧急采购，3分钟左右您将得到回复。