LTC3524

1

3524f

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

Adjustable TFT Bias Supply

with WLED Driver

converter solution for small/medium-sized polysilicon thin

film transistor (TFT) liquid crystal (LCD) display panels.

The device operates from a single Lithium-Ion/polymer

battery or any voltage source between 2.5V and 6V.

A 1.5MHz synchronous boost converter generates a pro-

grammable low noise, high efficiency 25mA TFT supply

of up to 6.0V. Regulated, low ripple charge pumps are

used to generate up to +20V and –20V at 2mA. Output

sequencing is internally controlled to insure proper

initialization and rapid discharge of the LCD panel in

shutdown.

A second 1.5MHz boost converter powers one or two LED

strings with up to five series elements each. LED current

and display brightness can be controlled over a wide range

using analog or digital means up to 25mA.

The LTC3524 is offered in the 4mm × 4mm 24-pin QFN

package, minimizing the total solution footprint.

+5V, –7.5V, +12.5V, 8 LED Power Supply

■

Generates Three Adjustable, Low Noise Rails for

Small/Medium TFT Displays

■

Drives Up to Ten White LEDs

■

LED Dimming and Open-Circuit Protection

■

Controlled Power-Up/Power-Down Sequencing

■

1.5MHz Fixed Frequency, Low Noise Operation

■

■

TFT Supply Efficiency Up to 90%

■

LED Supply Efficiency Up to 78%

■

Two Independantly Enabled LED Strings

■

■

Tiny External Solution

■

24-Lead QFN Package (4mm × 4mm × 0.75mm)

■

PDAs, Palmtop Computers

■

Digital Still and Video Cameras

■

Handheld GPS

■

Portable Instrument Displays

■

Portable Media Players

LCD Bias and LED Efficiency

0.1

μF

–7.5V

2mA

10

μF

3.3

μH

10

μH

0.1

μF

3524 TA01a

SW2

FBVO

VNIN

V2x

VH

SW1

Li-Ion

VLED

LED2

LED1

PROG

ELED2

ELED1

ELCD

VN

FBN

FBH

GND

100k for 20mA

470k

1M

+

–

324k

220k

10

μF

0.1

μF

1M

+5V

25mA

+12.5V

2mA

+10V

0.47

μF

2M

0.47

μF

LTC3524

2.2

μF

0.47

μF

5

80

90

25

3524 TA01b

70

60

10

15

20

100

LCD

LED

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

True Color PWM is a registered trademarks of Linear Technology Corporation. All other

trademarks are the property of their respective owners.