Datasheet > LM3570SD

LM3570SD

更新时间： 2024-10-30 22:51:55

品牌	Logo	应用领域
美国国家半导体 - NSC		驱动器
页数	文件大小	规格书
13页	350K
描述
Low Noise White LED Driver System

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LM3570SD 数据手册

July 2004

LM3570

Low Noise White LED Driver System

General Description

Features

n 2.7V to 5.5V Input Voltage

The LM3570 device provides a complete LED driver solution

for wireless handsets and other portable devices using a

display and keypad. With three constant current sources, up

to three white LEDs can be used for display lighting with

excellent current matching (0.3% typ.). The regulated 4.35V

output voltage is perfect for driving auxiliary keypad LEDs in

voltage mode.

Regulated Output Voltage (V_OUT= 4.35V)

n Regulated I_Dxwith 0.3% matching between constant

current outputs

n High Efficiency 3/2 Boost function

Drives one, two, or three white LEDs with no bias

resistor losses

The LM3570 utilizes a high efficiency 3/2 CMOS charge-

pump with a pre-regulation loop that minimizes conducted

noise on the input. It accepts an input voltage range from

2.7V to 5.5V and maintains a constant current determined by

the current through an external R_SETresistor.

n Drives auxiliary keypad LEDS in voltage mode

n Up to 80mA total output current

n Active-High Enable

n Active-High PWM Control Pin for independent control of

current sources

n Very small solution size

n 1µA(max) shutdown current

n 500kHz switching frequency (typ.)

n Linear regulation generates predictable noise spectrum

The device supplies up to 80mA of total load current to

accommodate any combination of up to three white LEDs,

and additional current from V_OUT. The switching frequency is

set at 500kHz. (typ.) to keep the conducted noise spectrum

away from sensitive frequencies within portable RF devices.

LLP-14 package: 4.0mm X 3.0mm X 0.8mm

By applying a pulse width modulated (PWM) signal to the

PWM pin, the user has the ability to independently control

the brightness of the regulated current source outputs with- Applications

out shutting down the regulated output voltage.

n Portable devices using white or blue LEDs with display

and backlight or frontlight

n 1-Cell LiIon battery-operated equipment including PDAs,

hand-held PCs and cellular phones

Typical Application Circuit

20085021

DS200850

www.national.com

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