1 Features

1• High-Voltage DC/DC Boost Converter with

Integrated FET with Four Switching Frequency

Options: 156/312/625/1250 kHz

• 2.7-V to 22-V Input Voltage Range to Support 1x

to 5x Cell Li-Ion Batteries

• Programmable PWM Resolution

– 8 to 13 True Bits (Steady State)

– Additional 1 to 3 Bits Using Dithering During

Brightness Changes

• I2C and PWM Brightness Control

• Automatic PWM & Current Dimming for Improved

Efficiency

• PWM output frequency and LED Current set

through Resistors

• Optional Synchronization to Display VSYNC

Signal

• Six LED Outputs with LED Fault (Short/Open)

Detection

• Low Input Voltage, Overtemperature, Overcurrent

Detection, and Shutdown

• Minimum Number of External Components

2 Applications

• Notebook and Netbook LCD Display LED

Backlight

• LED Lighting

3 Description

The LP8550 is a white-LED driver with integrated

boost converter. It has six adjustable current sinks

which can be controlled by PWM input or with I2C- compatible serial interface. The boost converter has

adaptive output voltage control based on the LED

driver voltages. This feature minimizes the power

consumption by adjusting the voltage to lowest

sufficient level in all conditions.

LED outputs have 8-bit current resolution and up to

13-bit PWM resolution with additional 1- to 3-bit

dithering to achieve smooth and precise brightness control. Proprietary Phase Shift PWM control is used

for LED outputs to reduce peak current from the

boost converter, thus making the boost capacitors

smaller. The Phase Shifting scheme also eliminates

audible noise.

Automatic PWM dimming at lower brightness values

and current dimming at higher brightness values can

be used to improve the optical efficiency. Internal

EEPROM is used for storing the configuration data. This makes it possible to have minimum external

component count and make the solution very small.

The LP8550 has safety features which make it

possible to detect LED outputs with open or short

fault — low input voltage and boost overcurrent

conditions are monitored, and chip is turned off in

case of these events. Thermal de-rating function

prevents overheating of the device by reducing backlight brightness when set temperature has been

reached.