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SC4505

High Efficiency Boost Converter

for Backlight/Flash LED Driver

POWER MANAGEMENT

Description

Features

Applications

White LED power supplies

Flat screen LCD bias supplies

TFT bias supplies

Dual panel Handset/Liquid Crystal Display Monitor

Portable media players

Digital video cameras

Digital still cameras

The SC4505 is a high-frequency PWM current-mode step-

up switching regulator with an integrated 2A power tran-

sistor. Its high switching frequency (1MHz) allows the use

of tiny surface-mount external passive components. The

internal switch is rated at 36V which makes the con-

verter ideal for multiple LED series operation with opti-

mal current matching. Two programmable independent

current source structure allows dual panel LED backlight

and flash operation.

The operating frequency of the SC4505 is set at 1MHz.

The selected operating frequency gives the SC4505 de-

sign flexibility for size, cost and efficiency optimization.

The SC4505 is available in thermally enhanced 16-pin

MLPQ package (3x3x0.9mm) with embedded over tem-

perature protection.

Typical Application Circuit

Two independent current sources for dual LED strands

with optimal current/light matching. Backlight up to

75mA, Flash up to 125mA

Wide input range from 2.6V to 12V

Adaptive output voltage up to 28V with OVP protec-

tion against open circuit conditions

Low shutdown current (<1

µA )

Internal Flash/Torch mode with flash timeout to pro-

tect LEDs

1MHz Fixed Frequency Current-Mode Control

Internal 2A current limit for driving large numbers of

LEDs

Supports PWM Dimming from 50Hz to 50kHz

Internal undervoltage lockout

Small, low profile, thermally enhanced 16-MLPQ pack-

age is fully WEEE and RoHS compliant

Revision: December 15, 2006

Figure 1. SC4505 Application Circuit for Backlight and Flashlight LED Driver

All Capacitors are Ceramic.

Boost Converter Efficiency vs Input Voltage

(2 String of 3 LEDs @30mA)

77

79

81

83

85

87

2.5

3

3.5

4

4.5

5

Input Voltage (V)

C6

12n

C5

12n

FL_TRB

D3

LED

RO2SET

1.54k

0

D6

LED

D2

LED

0

C4

12n

EN_BL

D4

LED

AGND

Power

Ground

0

SC4505

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

PGND

PGND

SW

SW

VO

IO2

IO1

COMP

AGND

IO2SET

IO1SET

EN_BL

EN_FL

FL_TRB

FTO

VIN

Analog

Ground

C3

0.33uF

C1

2.2uF

0

C2

2.2u

0

(Optional)

EN_FL

D7

LED

RO1SET

6.98k

LED: SML-LX0603UWD

VIN: 2.6V ~ 6.0V

D1

10BQ015

2

1

L1

IHLP-2525CZ-01-1R5-M-01

(Optional)

D5

LED

R1

1.47k

PGND

0