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Step-Up DC/DC Converter-Backlight LED Driver

■GENERAL DESCRIPTION

The XC9116 series is a fixed frequency, constant current step-up DC/DC converter ideal for driving LEDs used in backlighting

applications such as cellular phones, PDAs and digital cameras.

Output voltage of up to 17.5V can be derived, therefore, four

white LEDs in series can be driven.

Since an LED current can be set by an external resistor when LEDs are in-series

connection, all white LEDs can be turned on equably.

A network of two parallel legs with three in each LED can be also

driven. Luminance of the LEDs is controlled by changing the duty cycle of a PWM signal applied to the CE pin.

Efficiency is

Ω is used. A low profile and small board area solution can be achieved using a chip coil and an ultra small

μF as a result of the high 1.0MHz switching frequency.

The 'B' type of XC9116 has an additional fault detection circuit. If the LEDs are disconnected or damaged, excess or run away

output voltage is prevented by stopping the drive of the internal MOSFET.

ETR0407-002

■APPLICATIONS

●For White LED drivers

●Mobile phones, PHS

●PDAs

●Digital still cameras

■FEATURES

Input Voltage Range

: 2.5V ~ 6.0V

Output Voltage Range

: Up to 17.5V externally set-up

: Reference voltage 0.2V +5%

Oscillation Frequency

: 1.0MHz,

±20%

ON Resistance

: 2.0

Ω

Efficiency

: 86% (XC9116B Type)

: 84% (XC9116D Type)

driving 3 white LEDs in series)

Control

: PWM control

Standby current

: ISTB=1.0

μA (MAX.)

Load Capacitor

: 0.22

μF, ceramic

Lx Limit Current

: 325mA

Lx Overvoltage Limit

: XC9116B series

No Lx Overvoltage Limit : XC9116D series

Package

: SOT-25 (SOT-23-5), USP-6B

■TYPICAL APPLICATION CIRCUIT

■TYPICAL PERFORMANCE

CHARACTERISTICS

●XC9116B Type

VIN

Lx

CE

FB

VSS

L:22uH

VLF3010A

VIN

CL

0.22uF

SD

XB0ASB03A1B

20mA

10ohm

2.5V~6.0V

CIN

1uF

100Hz to

10kHz