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SC622

LED Light Management Unit Charge Pump, 400mA Flash LED, Dual LDOs, and SemWire™ Interface

Semtech Corporation 

POWER MANAGEMENT

Features

„ Input supply voltage range — 3.0V to 5.5V

„ Charge pump modes — 1x, 1.5x and 2x

„ Flash LED — 400mA max in flash mode, 250mA max

continuous for spotlight

„ Two user-configurable 100mA low-noise LDO

regulators

„ Charge pump frequency — 250kHz

„ SemWireTM single wire interface — up to 75kbit/s

„ External flash control pin to sync with camera

„ Optional 1s flash time out

„ Automatic sleep mode (LEDs off ) — I = 100μA

Q

„ Low shutdown current — 0.1μA (typical)

„ Ultra-thin package — 3mm x 3mm x 0.6mm

„ Fully WEEE and RoHS compliant

Applications

„ Cellular phone flash

„ PDA flash

„ Camera I/O and core power

SC622

LED Light Management Unit

Charge Pump, 400mA Flash LED, Dual

LDOs, and SemWireTM Interface

Description

The SC622 is a high efficiency charge pump LED driver

using Semtech’s proprietary mAhXLifeTM technology.

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

battery applications.

The charge pump provides continuous or bursted current

to a flash LED using a dedicated flash driver current sink.

The load and supply conditions determine whether the

charge pump operates in 1x, 1.5x, or 2x mode. A flash-

timeout feature disables the flash if active for longer than

1 second. The SC622 also provides two low-dropout, low-

noise linear regulators for powering a camera module or

other peripheral circuits.

The SC622 uses the proprietary SemWireTM single wire

interface. The interface controls all functions of the device,

including flash current and two LDO voltage outputs. The

single wire implementation minimizes microcontroller

and interface pin counts. The flash/spotlight output is

triggered via either the SemWire interface or a dedicated

pin.

In sleep mode, the device reduces quiescent current to

100μA while continuing to monitor the serial interface.

The two LDOs can be enabled when the device is in sleep

mode. Total current reduces to 0.1μA in shutdown.

Typical Application Circuit

VBAT

CIN

2.2μF

SemWire

Interface

Flash

Control

VIN

VOUT

SWIF

FLEN SC622

COUT

4.7μF

FLASH

July 19, 2007

CBYP

22nF

BYP

GREF

AGND

PGND

FL

LDO1

LDO2

VLDO1 = 2.5V to 3.3V

VLDO2 = 1.5V to 1.8V

C1+ C1- C2+ C2-

C1

2.2μF

C2

2.2μF

CLDO1

1.0μF

CLDO2

1.0μF

© 2007 Semtech Corporation

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

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