LP8551 datasheet(11/47 Pages) TI1

11 / 47 page

BOOST

LED

DRIVERS

LOGIC

EEPROM

C /

INTERFACE

LDO

OSC

TSD

PWM

DETECTOR

VLDO

GND_SW

GND_LED

PWM

VDDIO

SCLK

SDA

OUT1

OUT2

OUT3

OUT4

PLL

FAULT

VIN

TEMP

SENSOR

MCU

ISET

FSET

RISET

RFSET

GNDs

VBATT

LP8551

www.ti.com

SNVS673E – APRIL 2010 – REVISED SEPTEMBER 2014

8 Detailed Description

8.1 Overview

The LP8551 is a high-voltage LED driver for medium sized LCD backlight applications. It includes high-voltage

boost converter. Boost voltage automatically sets to the correct level needed to drive the LED strings. This is

done by monitoring LED output voltage drop in real time.

Four constant current sinks with PWM control are used for driving LEDs. Constant current value is set with

EEPROM bits and with RISET resistor. Brightness (PWM) is controlled either with I

2C register or with PWM input.

PWM frequencies are set with EEPROM bits and with RFSET resistor. Special Phase-Shift PWM mode can be

used to reduce boost output current peak, thus reducing output ripple, capacitor size, and audible noise.

Safety features include LED fault detection with open and short detection. LED fault detection prevents system

overheating in case of open in some of the LED strings. Chip internal temperature is constantly monitored and,

based on this, the LP8551 can reduce the brightness of the backlight to reduce thermal loading once certain trip

point is reached. Threshold is programmable in EEPROM. If chip internal temperature reaches too high, the

boost converter and LED outputs are completely turned off until the internal temperature has reached acceptable

level. Boost converter is protected against too high load current and over-voltage. The LP8551 notifies the

system about the fault through I2C register and with FAULT pin.

EEPROM programmable functions include:

•

PWM frequencies

•

Phase shift PWM mode

•

LED constant current

•

Boost output frequency

•

Temperature thresholds

•

Slope for brightness changes

•

PWM output resolution

•

Boost control bits

External components RISET and RFSET can also be used for selecting the output current and PWM frequencies.

8.2 Functional Block Diagram

Submit Documentation Feedback

Product Folder Links: LP8551

LP8551 Datasheet(PDF) 11 Page - Texas Instruments

LP8551 Datasheet(HTML) 11 Page - Texas Instruments

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

Datasheet Download

Link URL