SC657ULTRT Semtech, SC657ULTRT Datasheet

SC657ULTRT

Manufacturer Part Number

SC657ULTRT

Description

Backlight Driver For 5 LEDs With SemPulseTM Interface

Manufacturer

Semtech

Datasheet

1.SC657.pdf (22 pages)

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POWER MANAGEMENT

Features



Applications



Typical Application Circuit

April 3, 2009

Input supply voltage range — 2.9V to 5.5V

Very high efficiency charge pump driver system with

three modes — x, .5x and 2x

Five programmable current sinks — 0mA to 25mA

Up to three LED grouping options

Fade-in/fade-out feature for main LED bank

Charge pump frequency — 250kHz

SemPulse single wire interface

Backlight current accuracy — ±.5% typical

Backlight current matching — ±0.5% typical

LED float detection

Automatic sleep mode (LEDs off )

Shutdown current — 0.µA (typical)

Ultra-thin package — 2 x 2 x 0.6 (mm)

Fully WEEE and RoHS compliant

Cellular phones, smart phones, and PDAs

LCD modules

Portable media players

Digital cameras

Personal navigation devices

Display/keypad backlighting and LED indicators

BAT

2.2µF

= 2.9 to 5.5V

SemPulse

Interface

—

2.2µF

C1+

SPIF

GND

= 60µA (typ.)

C1-

SC657

C2+

OUT

C2-

BL1

BL2

BL3

BL4

BL5

2.2µF

Description

The SC657 is a high efficiency charge pump LED driver

using Semtech’s proprietary charge pump technology.

Performance is optimized for use in single-cell Li-ion

battery applications.

The charge pump provides backlight current utilizing five

matched current sinks. The load and supply conditions

determine whether the charge pump operates in x, .5x,

or 2x mode. An optional fading feature that gradually

adjusts the backlight current is provided to simplify

control software.

The SC657 uses the proprietary SemPulse

interface to control all functions of the device, including

backlight currents. The single wire interface minimizes

microcontroller and interface pin counts. The five LEDs

can be grouped in up to three separate banks that can be

independently controlled.

The SC657 enters sleep mode when all the LED drivers are

disabled. In this mode, the quiescent current is reduced

while the device continues to monitor the SemPulse

interface.

With a 2 x 2 (mm) package and four small capacitors, the

SC657 provides a complete LED driver solution with a

minimal PCB footprint.

2.2µF

OUT

Backlight Driver for 5 LEDs

with SemPulse

US Patents: 6,504,422; 6,794,926

Interface

SC657

single wire

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