MCU

LP8550

SW

FB

VLDO

GNDs

EN

ISET

VDDIO

PWM

SCLK

SDA

OUT1

OUT2

OUT3

OUT4

OUT5

OUT6

L1

D1

10V ± 40V

5.5V ± 22V

FILTER

5V

FSET

15 éH

VSYNC

210 mA ± 400 mA

COUT

CIN

10 éF

4.7 éF

CVLDO

1 éF

VDDIO reference voltage

VSYNC signal

120 k

#

100 nF

1 éF

FAULT

Can be left floating

if not used

39 pF

VIN

RISET

RFSET

VBATT

0

10 20 30 40 50 60 70 80 90 100

60

65

70

75

80

85

90

95

100

DUTY CYCLE (%)

VIN = 9V

VIN = 12V

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LP8550

SNVS657E – SEPTEMBER 2010 – REVISED SEPTEMBER 2014

LP8550 High-Efficiency LED Backlight Driver for Notebooks

1 Features

3 Description

The LP8550 is a white-LED driver with integrated

1

•

High-Voltage DC/DC Boost Converter with

boost converter. It has six adjustable current sinks

Integrated FET with Four Switching Frequency

which can be controlled by PWM input or with I2C-

Options: 156/312/625/1250 kHz

compatible serial interface. The boost converter has

•

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

adaptive output voltage control based on the LED

to 5x Cell Li-Ion Batteries

driver voltages. This feature minimizes the power

consumption by adjusting the voltage to lowest

•

Programmable PWM Resolution

sufficient level in all conditions.

–

8 to 13 True Bits (Steady State)

LED outputs have 8-bit current resolution and up to

–

Additional 1 to 3 Bits Using Dithering During

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

Brightness Changes

dithering to achieve smooth and precise brightness

•

I2C and PWM Brightness Control

control. Proprietary Phase Shift PWM control is used

•

Automatic PWM & Current Dimming for Improved

for LED outputs to reduce peak current from the

Efficiency

boost converter, thus making the boost capacitors

smaller. The Phase Shifting scheme also eliminates

•

PWM output frequency and LED Current set

audible noise.

through Resistors

Automatic PWM dimming at lower brightness values

•

Optional Synchronization to Display VSYNC

and current dimming at higher brightness values can

Signal

be used to improve the optical efficiency. Internal

•

Six LED Outputs with LED Fault (Short/Open)

EEPROM is used for storing the configuration data.

Detection

This makes it possible to have minimum external

•

Low Input Voltage, Overtemperature, Overcurrent

component count and make the solution very small.

Detection, and Shutdown

The LP8550 has safety features which make it

•

Minimum Number of External Components

possible to detect LED outputs with open or short

fault — low input voltage and boost overcurrent

2 Applications

conditions are monitored, and chip is turned off in

case of these events. Thermal de-rating function

•

Notebook and Netbook LCD Display LED

prevents overheating of the device by reducing

Backlight

backlight brightness when set temperature has been

•

LED Lighting

reached.

Device Information(1)

PART NUMBER

PACKAGE

BODY SIZE (MAX)

LP8550

DSBGA (25)

2.49 x 2.49 mm

(1) For all available packages, see the orderable addendum at

the end of the datasheet.

Simplified Schematic

LED Efficiency

1

An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,

intellectual property matters and other important disclaimers. PRODUCTION DATA.