AL3158

HIGH EFFICIENCY 1x/2x CHARGE PUMP

FOR WHITE LED APPLICATIONS

AL3158

Document number: DS35047 Rev. 2 - 2

6 of 10

www.diodes.com

January 2011

© Diodes Incorporated

Functional Description

The AL3158 is a dual-mode high efficiency charge pump

(1x and 2x) device, driving three groups of three LED

channels at 30mA maximum each, intended for white LED

backlight applications.

An internal comparator circuit

compares the voltage at each constant current sink input

against a reference voltage. To ensure maximum power

efficiency, the most appropriate switching mode (1x and

2x) is automatically selected.

The AL3158 requires only three external components: one

2.2µF

ceramic

input

capacitor

and

one

The each output channel of the AL3158 can drive three

groups of three individual LED channels with a maximum

current of fixed manufacture setting (20mA or 30mA) per

channel. These can be paralleled to give a total output

current of 270mA.

Disabled Current Sinks

Unused current channels must be disabled by connecting

the sinks to VOUT with only a small sense current flowing

through the disabled channel.

Soft-Start

Soft-start is incorporated to prevent excessive inrush

current during power-up, mode switching, and transitioning

out of stand-by mode.

Short-Circuit Protection

Short-circuit protection function is incorporated to prevent

excessive load current when either flying cap terminals or

output pin electrically tied to a very lower voltage or

ground.

Over-Voltage Protection

Over-Voltage Protection function is incorporated to limit

the output voltage under a safe value to avoid on-chip

device breakdown.

Under-Voltage Lockout

Under-Voltage lockout feature disables the device when

the input voltage drops below UVLO threshold.

Thermal Auto Shutdown

When the die temperature exceeds the thermal limit, the

device will be disabled and enter stand-by mode. The

operation resumes whenever the die cools off sufficiently.

PWM Dimming Control

The AL3158 provides simple PWM dimming control

through ENx pins, and the current is adjusted by the duty

cycle of the signal applied on ENx pin. The recommended

PWM frequency is from 200Hz to 50KHz depending on

applications.

EN<3:1>

LED ON/OFF CONTROL

XX0

LED1~LED3 OFF

XX1

LED1~LED3 ON

X0X

LED4~LED6 OFF

X1x

LED4~LED6 ON

0XX

LED7~LED9 OFF

1xX

LED7~LED9 ON