80

82

84

86

88

90

0

20

40

60

80

100

Brightness [%]

6p8s

6p6s

6p4s

C001

VIN

LP8557

FB

SW

1.1 ” VOUT / VIN ” 11

L1

D1

VDD

CIN

COU

T

LED1

LED2

LED3

LED4

LED5

LED6

GNDs

ISET

FSET

2.7 V ± 5.5 V

7 V ± 28 V

PWM

PWM

VOUT

RFSET

RISET

Product

Folder

Sample &

Buy

Technical

Documents

Tools &

Software

Support &

Community

LP8557, LP85571

SNVSA15B – DECEMBER 2013 – REVISED DECEMBER 2015

LP8557 High-Efficiency LED Backlight Driver For Tablets

1 Features

3 Description

The LP8557 and LP8557I are high-efficiency LED

1

•

High-Efficiency DC-DC Boost Converter With 28-V

drivers each featuring an integrated DC-DC inductive

Integrated Power MOSFET

boost converter and six high-precision current sinks.

•

2.7-V to 5.5-V VDD Range for Supporting Single-

LP8557 is intended for applications that exclusively

Cell Li-Ion Battery Applications

use a pulse width modulated (PWM) signal for

controlling the brightness while LP8557I is intended

•

Six 25-mA High-Precision LED Current Sinks

for applications that can utilize an I2C master as well.

•

Adaptive Boost Voltage and LED Current Sink

Headroom Controls for Maximum System

The boost converter has adaptive output voltage

Efficiency

control.

This

feature

minimizes

the

power

consumption by adjusting the voltage to the lowest

•

LED String Count Auto-Detect for Maximum

sufficient level under all conditions.

Design Flexibility

The adaptive current sink headroom voltage control

•

Smart Phase Shift PWM Mode for Reduced

scales the headroom voltage with the LED current for

Audible Noise

optimal system efficiency.

•

PWM Input Duty Cycle Brightness Control, PWM

The LED string auto-detect function enables use of

Output Frequency Selectable Independent of

the same device in systems with 1 to 6 LED strings

Input Frequency

for the maximum design flexibility.

•

Hybrid PWM Plus Current Dimming for Higher

LED Drive Optical Efficiency

Proprietary hybrid PWM plus current mode dimming

enables additional system power savings. Phase-shift

•

Switching Frequency, PWM Output Frequency,

PWM allows reduced audible noise and smaller boost

and LED Current can be set Through Resistors or

output capacitors.

I2C Interface

Flexible CABC support combines brightness level

•

Programmable Boost SW Slew Rate Control and

selections

based

on

the

PWM

input

and

I2C

Spread Spectrum Scheme for Reduced Switching

commands.

Noise and Improved EMI Performance

•

UVLO, TSD, BST_OVP, BST_OCP, BST_UV,

Device Information(1)

LED OPEN* and LED Short Fault Coverage

PART NUMBER

PACKAGE

BODY SIZE (MAX)

•

Minimum Number of External Components

LP8557

DSBGA (16)

1.906 mm x 1.64 mm

LP8557I

2 Applications

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

Tablet LCD Display LED Backlight

the end of the data sheet.

Simplified Schematic With PWM-Only Option

LED Efficiency With 6 LED Strings

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.