Four-String White LED Driver

Data Sheet

ADD5205

Rev. 0

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FEATURES

White LED driver based on inductive boost converter

Input voltage range: 2.8 V to 18 V

Internal compensation

1 MHz fixed operating frequency

28 V fixed overvoltage protection

Built-in soft start for boost converter

Drives up to 4 LED current sources

LED current adjustable up to 25 mA for each channel

DC current level brightness control with PWM input

LED open fault protection

General

Thermal shutdown

Undervoltage lockout

12-lead, 3 mm × 3 mm × 0.75 mm LFCSP package

APPLICATIONS

Smart PCs, PMPs, tablet PCs, UMPCs, and notebooks

FUNCTIONAL BLOCK DIAGRAM

STEP-UP SWITCHING REGULATOR

4-CHANNEL CURRENT SOURCES

BRIGHTNESS CONTROL LOGIC

UNDERVOLTAGE LOCKOUT

SOFT START

THERMAL PROTECTION

OVERVOLTAGE PROTECTION

AUTODISABLE FOR LED OPEN

Figure 1.

GENERAL DESCRIPTION

The ADD5205 is a white LED driver for backlight applications

based on high efficiency, current mode, step-up converter

technology. It is designed with a 0.3 Ω internal switch and 1 MHz

fixed operating frequency. The ADD5205 contains four regulated

constant current sources for uniform brightness intensity. Each

current source is capable of driving up to 25 mA.

The ADD5205 has four parallel strings of multiple series connected

LEDs with ±2% current matching. The device provides adjustable

current sources that drive up to 25 mA using an external resistor.

The LED current can be controlled by a PWM signal input on

the PWM pin. An internal circuit translates the PWM signal to

an analog signal with an external capacitor and linearly controls

the LED current.

The ADD5205 has multiple safety protection features to prevent

any damage during fault conditions. If one or more LEDs are open,

the device disables the faulty current regulator automatically.

The internal soft start prevents inrush current during startup. A

thermal shutdown protection feature prevents thermal damage.

The ADD5205 is available in a low profile, thermally enhanced

3 mm × 3 mm × 0.75 mm, 12-lead lead frame chip scale package

(LFCSP) and is specified over the temperature range of −25°C

to +85°C.