目录qaf嘉泰姆

1.产品概述                       2.产品特点qaf嘉泰姆
3.应用范围                       4.下载产品资料PDF文档 qaf嘉泰姆
5.产品封装图                     6.电路原理图                   qaf嘉泰姆
7.功能概述                        8.相关产品qaf嘉泰姆

一,产品概述(General Description)    qaf嘉泰姆

   The CXLE8856 is a set-up DC-DC converter that delivers a regulated output current. The device switches at a 1.0MHz constant frequency, allowing for theqaf嘉泰姆
use of small value external inductor and ceramic capacitors.The CXLE8856 is targeted to be used for driving loads up to 1A from a two-cell alkaline battery.qaf嘉泰姆
    The LED current can be auto adjusted by internal smart module and programmed by the external current sense resistor, Rs,connected between the feedback pin (FB) and ground. A low 95mV(TYP.) feedback voltage reduces the powerqaf嘉泰姆
loss in the Rs for better efficiency. With its internal 2A,100mΩ NMOS switch, the device can provide high efficiency even at heavy load. During the shutdownqaf嘉泰姆
mode, the feedback resistor Rs and the load are completely disconnected and the current consumption is reduced to 1uA.The CXLE8856 is available in the 6-leadqaf嘉泰姆
SOT-23-6L package.qaf嘉泰姆
二.产品特点(Features)qaf嘉泰姆

LED Power Efficiency: up to 90%qaf嘉泰姆
Current Accuracy: 5%(Vin =3.6V to 1.8Vqaf嘉泰姆
@Vf =3.7V)qaf嘉泰姆
Low Start-Up Voltage: 0.9Vqaf嘉泰姆
Low Hold Voltage:0.75Vqaf嘉泰姆
1MHz Switching Frequencyqaf嘉泰姆
Uses small, Low Profile External Componentsqaf嘉泰姆
Low RDS(ON) : 100mΩ (TYP.)qaf嘉泰姆
Over Temperature Protectionqaf嘉泰姆
Low Profile SOT-23-6L Packageqaf嘉泰姆
三,应用范围 (Applications)qaf嘉泰姆

White LED Torch (Flashlight)qaf嘉泰姆
White LED Camera Flashqaf嘉泰姆
DSC(Digital Still Camera)Flashqaf嘉泰姆
Cellular Camera Phone Flashqaf嘉泰姆
PDA Camera Flashqaf嘉泰姆
Camcorder Torch(Flashlight) Lampqaf嘉泰姆
四.下载产品资料PDF文档 qaf嘉泰姆

需要详细的PDF规格书请扫一扫微信联系我们，还可以获得免费样品以及技术支持！qaf嘉泰姆

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五,产品封装图 (Package)qaf嘉泰姆

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六.电路原理图qaf嘉泰姆

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七,功能概述qaf嘉泰姆

Inductor Selectionqaf嘉泰姆
The CXLE8856 can use small value inductors due to its switching frequency of 1MHz. The value of inductor will focus in the range of 2.2uH to 4.7uH for most CXLE8856 applications. In typical high current white LED applications,it is recommended to use a 4.7uH inductor. The inductor should have low DCR (DC resistance) to minimize the IR power loss, and it requires a current rating of 2A to handle the peak inductor current without saturating. qaf嘉泰姆
Capacitor Selectionqaf嘉泰姆
An input capacitor is required to reduce the input ripple and noise for proper operation of the CXLE8856. For good input decoupling,  Low  ESR(equivalent  series  resistance) capacitors should be used at the input. At least 2.2uF input capacitor  is  recommended  for  most  applications. A minimum output capacitor value of 6.8uF is recommended under normal operating conditions, while a 10uF-22uF capacitor may be required for higher power LED current. A reasonable value of the output capacitor depends on the LED current. The ESR of the output capacitor is the important parameter to determine the output voltage ripple of the converter, so low ESR capacitors should be used at the output to reduce the output voltage ripple. The small size of ceramic capacitors is an excellent choice for CXLE8856 applications. The X5R and X7R types are preferred because they maintain capacitance over wide voltage and temperature ranges.qaf嘉泰姆
Diode Selectionqaf嘉泰姆
It's indispensable to use a Schottky diode rated at 2A with the CXLE8856. Using a Schottky diode with a lower forward voltage drop is better to improve the power LED efficiency, and its voltage rating should be greater than the output voltage. In application, the ON Semiconductor MBRA210LT3G is recommended. qaf嘉泰姆
LED Current Settingqaf嘉泰姆
The LED current is set by the single external Rs resistor connected to the FB pin as shown in the typical application circuit on page 1. The typical FB reference is internally regulated to 95mV(TYP.). The LED current is 95mV/Rs. It's recommended to use a 1% or better precision resistor for the better LED current accuracy.qaf嘉泰姆
The formula and table 1 for Rs selection are shown as follows:qaf嘉泰姆
Rs=95mV/ILEDqaf嘉泰姆
PCB Layout Guidelinesqaf嘉泰姆
For best performance of the CXLE8856, the following guidelines must be strictly followed. Input and Output capacitors should be placed close to the IC and connected to ground plane to reduce noise coupling.Keep the main current traces as possible as short and wide.SW node of DC-DC converter is with high frequency voltage swing. It should be kept at a small area.Place the feedback components as close as possible to the IC and keep away from the noisy devices.qaf嘉泰姆
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