LP8543SQE/NOPB - National Semiconductor

LP8543

LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight

Literature Number: SNVS604C

LP8543

November 14, 2011

SMBus/I2C Controlled WLED Driver for Medium-Sized LCD

Backlight

General Description

The LP8543 is a white LED driver with integrated boost con-

verter. It has 7 adjustable current sinks which can be con-

trolled by SMBus or I2C-compatible serial interface, PWM

input and Ambient Light Sensor (ALS).

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 suffi-

cient level in all conditions. Phase Shift PWM dimming offers

further power saving especially when there is poor matching

in the forward voltages of the LED strings. Boost voltage can

also be controlled through the SMBus/I2C.

Internal EEPROM stores the data for backlight brightness and

ambient light sensor calibration. Brightness can be calibrated

during the backlight unit production so that all units produce

the same brightness. EEPROM also stores the coefficients

for the LED control equations and the default LED current

value. LED current has 8–bit adjustment from 0 to 60 mA.

The LP8543 has several safety and diagnostic features. Low-

input voltage detection turns the chip off if the system gets

stuck and battery fully discharges. Input voltage detection

threshold is adjustable for different battery configurations.

Thermal regulation reduces backlight brightness above a set

temperature. LED fault detection reports open or LED short

fault. Boost over-current fault detection protects the chip in

case of over-current event.

LP8543 is available in the LLP 24-pin package.

Features

■High-voltage DC/DC boost converter with integrated FET

■5.5V to 22V input voltage range to support 2x, 3x and 4x

Li-Ion batteries.

■PWM phase shift control with adaptive boost output to

increase efficiency compared to conventional boost

converters topologies

■PWM brightness control for single wire control and stand-

alone use

■Digital Ambient light sensor interface with user-

programmed ambient light to backlight brightness curve

■Easy-to-use EEPROM calibration for current, intensity and

ambient light response setting

■Seven LED drivers with LED fault (short/open) detection

■Eight-bit LED current control

■Internal thermal protection and backlight safety dimming

feature

■Two wire, SMBus/ I2C-compatible control interface

■Low-input voltage detection and shutdown

■Minimum number of external components

■LLP 24-pin package, 4 x 4 x 0.8 mm

Applications

■Medium sized (>10 inches) LCD Display Backlight

■LED Lighting

Typical Application

30085870

LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight

Typical Application, Using 7 Outputs for Display1

30085871

Typical Application, Stand-Alone Mode

30085869

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LP8543

Connection Diagrams and Package Mark Information

24–pin Leadless Leadframe Package (LLP)

4.0 x 4.0 x 0.8mm, 0.5 mm pitch

NS Package Number SQA24A

30085872

Bottom View

30085875

Top View

Package Mark

30085896

Package Mark - Top View

U = Fab

Z = Assembly

XY = 2–Digit Date Code

TT = Die Traceability

L8543SQ = Product Identification

Ordering Information

Order Number Spec/flow Package Marking Supplied As

LP8543SQX HFLF L8543SQ 4500 units, Tape-and-Reel

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LP8543

Pin Descriptions

Pin # Name Type Description

1 GND_SW G Boost ground

2 PWM I PWM dimming input. This pin must be connected to GND if not used.

3 IF_SEL I Serial interface mode selection: IF_SEL= Low for I2C-compatible interface and

IF_SEL=High for SMBus interface.

4 EN I Enable input pin

5 ALSI I Ambient light sensor frequency input pin. This pin must be connected to GND if ALS is

not used.

6 ALSO O Ambient light sensor enable output

7 FAULT OD Fault indication output

8 VDDIO PDigital IO reference voltage 1.65V to 5.5V. Needed in SMBus/I2C and stand alone mode.

9 GND_S G Signal ground

10 SCLK I Serial clock. This pin must be connected to GND if not used.

11 SDA I/O Serial data. This pin must be connected to GND if not used.

12 OUT1 A Current sink output

13 OUT2 A Current sink output

14 OUT3 A Current sink output

15 GND_L G Ground for current sink outputs

16 OUT4 A Current sink output

17 OUT5 A Current sink output. Can be left floating if not used.

18 OUT6 A Current sink output. Can be left floating if not used.

19 OUT7 A Current sink output. Can be left floating if not used.

20 ADR I Serial interface address selection. See serial interface chapter for details. This pin must

be connected to GND if not used.

21 FB A Boost feedback input

22 VLDO A LDO output voltage. 470 nF capacitor should be connected to this pin.

23 VIN P Input power supply 5.5V to 22V

24 SW A Boost switch

A: Analog Pin, G: Ground Pin, P: Power Pin, I: Input Pin, I/O: Input/Output Pin, O: Output Pin, OD: Open Drain Pin

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LP8543

Absolute Maximum Ratings (Note 1, Note

If Military/Aerospace specified devices are required,

please contact the Texas Instruments Sales Office/

Distributors for availability and specifications.

VIN -0.3V to +24.0V

VDDIO, VLDO -0.3V to +6.0V

Voltage on Logic Pins (PWM, ADR

EN, IF_SEL, ALSO, ALSI)

-0.3V to +6.0V

Voltage on Logic Pins (SCLK, SDA,

FAULT)

-0.3V to VDDIO

V (OUT1...OUT7 SW, FB) -0.3V to +44.0V

Continuous Power Dissipation

(Note 3)

Internally Limited

Junction Temperature (TJ-MAX) 125°C

Storage Temperature Range -65°C to +150°C

Maximum Lead Temperature

(Soldering)

(Note 4)

ESD Rating

Human Body Model:

Machine Model:

(Note 5)

2 kV

OUT7: 150V

All other pins : 200V

Operating Ratings (Note 1, Note 2)

Input Voltage Range VIN 5.5 to 22.0V

VDDIO 1.65 to 5V

V (OUT1...OUT7, SW, FB) 0 to 40V

Junction Temperature (TJ) Range −40°C to +125°C

Ambient Temperature (TA) Range

(Note 6) −40°C to +85°C

Thermal Properties

Junction-to-Ambient Thermal

Resistance (θJA), SQA Package

(Note 7) 35 - 50°C/W

Electrical Characteristics (Note 2, Note 8)

Limits in standard typeface are for TA = 25°C. Limits in boldface type apply over the full operating ambient temperature range

(−40°C < TA < +85°C). Unless otherwise specified: VIN = 12.0V, VDDIO = 2.8V, CVLDO = 470 nF, L1 = 15 μH, CIN = 10 μF, COUT =

4.7 μF. (Note 9)

Symbol Parameter Condition Min Typ Max Units

IIN

Standby supply current Internal LDO disabled

EN=L and PWM=L

1μA

Normal mode supply current LDO enabled, boost enabled, no current

going through LED outputs

3.5 mA

fOSC Internal Oscillator Frequency

Accuracy

-4

-7

VLDO Internal LDO Voltage 4.5 5.0 5.5 V

ILDO Internal LDO External Loading 5.0 mA

Boost Converter Electrical Characteristics

Symbol Parameter Condition Min Typ Max Units

RDS-ON Switch ON resistance ISW = 0.5A 0.12 Ω

VMAX Boost maximum output voltage 38 V

ILOAD

Maximum Continuous Load

Current

VIN ≥ 12V, VOUT = 38V

VIN = 5.5V, VOUT = 38V

400

180 mA

fSW Switching Frequency BOOST_FREQ_SEL = 0

BOOST_FREQ_SEL = 1

625

1250

kHz

VOV Over-voltage protection voltage VBOOST = 38V

VBOOST < 38V

VBOOST + 1.6V

VBOOST + 4V

tPULSE Switch pulse minimum width no load 50 ns

tDELAY

Startup delay EN_STANDALONE = 1, PWM input

active, EN is set from low to high

2 ms

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LP8543

Symbol Parameter Condition Min Typ Max Units

tSTARTUP Startup time (Note 10) 8 ms

IMAX SW pin current limit

IMAX_SEL[1:0] = 00

IMAX_SEL[1:0] = 01

IMAX_SEL[1:0] = 10

IMAX_SEL[1:0] = 11

0.9

1.4

2.0

2.5

LED Driver Electrical Characteristics

Symbol Parameter Condition Min Typ Max Units

ILEAKAGE Leakage current Outputs OUT1 to OUT7 (Voltage on pins

40V) -1 1µA

IMAX Maximum Source Current Outputs OUT1 to OUT7 60 mA

IOUT

Output current accuracy

(Note 11)Output current set to 20 mA -3

-4

IMATCH Matching OUT1-7 (Note 11) Output current set to 20 mA 0.8 1.5 %

IMATCH Matching OUT1-6 (Note 11) Output current set to 20 mA 0.5 1.35 %

PWMRES PWM output resolution

fPWM_OUT ≤ 4883 Hz 10

bit

fPWM_OUT = 9766Hz 9

fPWM_OUT = 19531Hz 8

fLED

Min LED Switching Frequency

PWM_FREQ[2:0] = 000b

PSPWM_FREQ[1:0] = 00b,

PWM_MODE = 0

-4%

-7% 229 4%

Max LED Switching Frequency

PWM_FREQ[2:0] = 111b,

PSPWM_FREQ[1:0] = 11b,

PWM_MODE = 0

-4%

-7% 19531 4%

VSAT Saturation voltage (Note 12)

Output current set to 20 mA 200 270

330 mV

Output current set to 60 mA 300 400

540

Ambient Light Sensor Interface Characteristics

Symbol Parameter Condition Min Typ Max Units

fALS

ALS Frequency Range 0.2 2000 kHz

ALS Duty Cycle 40 60 %

tCONV Conversion Time 500 ms

PWM Interface Characteristics

Symbol Parameter Condition Min Typ Max Units

fPWM PWM Frequency Range 0.1 25 kHz

tSTBY Turn Off Delay PWM input low time for turn off, stand-alone

mode, slope disabled 50 ms

tPULSE PWM Input Pulse Width 200 ns

PWMRES PWM input resolution fPWM_IN < 4.5 kHz 10 bit

fPWM_IN = 20 kHz 8

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LP8543

Under-Voltage Protection

Symbol Parameter Condition Min Typ Max Units

VUVLO UVLO Threshold Voltage

UVLO_THR = 1, falling 2.55 2.70 2.94

UVLO_THR = 1, rising 2.62 2.76 3.00

UVLO_THR = 0, falling 5.11 5.40 5.68

UVLO_THR = 0, rising 5.38 5.70 5.98

Logic Interface Characteristics

Symbol Parameter Condition Min Typ Max Units

Logic Input PWM

VIL Input Low Level 0.4 V

VIH Input High Level 2.2 V

IIInput Current -1.0 1.0 µA

Logic Input EN

VIL Input Low Level 0.4 V

VIH Input High Level 1.2 V

IIInput Current -1.0 1.0 µA

Logic Input SCLK, SDA, ADR, ALSI, IF_SEL

VIL Input Low Level 0.2xVDDIO V

VIH Input High Level 0.8xVDDIO V

IIInput Current -1.0 1.0 µA

Logic Outputs SDA, FAULT

VOL Output Low Level IOUT = 3 mA (pull-up current) 0.3 0.5 V

ILOutput Leakage Current VOUT = 2.8V -1.0 1.0 µA

Logic Output ALSO

VOL Output Low Level IOUT = 3 mA (pull-up current) 0.3 0.5 V

VOH Output High Level IOUT = –3 mA (pull-up current) VLDO - 0.5V VLDO - 0.3V V

ILOutput Leakage Current VOUT = 2.8V -1.0 1.0 µA

I2C Serial Bus Timing Parameters (SDA, SCLK) (Note 13)

Symbol Parameter Limit Units

Min Max

fSCLK Clock Frequency 400 kHz

1 Hold Time (repeated) START Condition 0.6 µs

2 Clock Low Time 1.3 µs

3 Clock High Time 600 ns

4 Setup Time for a Repeated START Condition 600 ns

5 Data Hold Time 50 ns

6 Data Setup Time 100 ns

7 Rise Time of SDA and SCL 20+0.1Cb300 ns

8 Fall Time of SDA and SCL 15+0.1Cb300 ns

9 Set-up Time for STOP condition 600 ns

10 Bus Free Time between a STOP and a START Condition 1.3 µs

Capacitive Load for Each Bus Line

Load of 1 pF corresponds to 1 ns. 10 200 ns

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LP8543

30085898

SMBus Timing Parameters (SDA, SCLK) (Note 13, Note 14)

Symbol Parameter Limit Units

Min Max

fSCLK Clock Frequency 10 100 kHz

1 Hold Time (repeated) START Condition 4.0 µs

2 Clock Low Time 4.7 µs

3 Clock High Time 4.0 50 µs

4 Setup Time for a Repeated START Condition 4.7 µs

5 Data Hold Time 300 ns

6 Data Setup Time 250 ns

7 Rise Time of SDA and SCL 1000 ns

8 Fall Time of SDA and SCL 300 ns

9 Set-up Time for STOP condition 4.0 µs

10 Bus Free Time between a STOP and a START Condition 4.7 µs

Capacitive Load for Each Bus Line

Load of 1 pF corresponds to 1 ns. 10 200 ns

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation

of the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions,

see the Electrical Characteristics tables.

Note 2: All voltages are with respect to the potential at the GND pins.

Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at TJ = 150°C (typ.) and disengages at TJ

= 130°C (typ.).

Note 4: For detailed soldering specifications and information, please refer to Texas Instruments AN1187: Leadless Leadframe Package (LLP).

Note 5: The Human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The machine model is a 200 pF capacitor discharged

directly into each pin. MIL-STD-883 3015.7

Note 6: In applications where high power dissipation and/or poor package thermal resistance is present, the maximum ambient temperature may have to be

derated. Maximum ambient temperature (TA-MAX) is dependent on the maximum operating junction temperature (TJ-MAX-OP = 125°C), the maximum power

dissipation of the device in the application (PD-MAX), and the junction-to ambient thermal resistance of the part/package in the application (θJA), as given by the

following equation: TA-MAX = TJ-MAX-OP – (θJA × PD-MAX).

Note 7: Junction-to-ambient thermal resistance is highly application and board-layout dependent. In applications where high maximum power dissipation exists,

special care must be paid to thermal dissipation issues in board design.

Note 8: Min and Max limits are guaranteed by design, test, or statistical analysis. Typical numbers are not guaranteed, but do represent the most likely norm.

Note 9: Low-ESR Surface-Mount Ceramic Capacitors (MLCCs) used in setting electrical characteristics.

Note 10: Start-up time is measured from the moment boost is activated until the VOUT crosses 90% of its target value.

Note 11: Output Current Accuracy is the difference between the actual value of the output current and programmed value of this current. Matching is the maximum

difference from the average. For the constant current sinks on the part (OUT1 to OUT7), the following are determined: the maximum output current (MAX), the

minimum output current (MIN), and the average output current of all outputs (AVG). Two matching numbers are calculated: (MAX-AVG)/AVG and (AVG-MIN/

AVG). The largest number of the two (worst case) is considered the matching figure. The typical specification provided is the most likely norm of the matching

figure for all parts. Note that some manufacturers have different definitions in use.

Note 12: Saturation voltage is defined as the voltage when the LED current has dropped 10% from the value measured at 2V.

Note 13: Guaranteed by design. VDDIO = 1.65V to 5.5V.

Note 14: The switching characteristics of the LP8543 fully meets or exceeds the published System Management Bus (SMBus) Specification Version 2.0.

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LP8543

Typical Performance Characteristics

Unless otherwise specified: VBATT = 12.0V, CVLDO = 470 nF, L1 = 15 μH, CIN = 10 μF, COUT = 4.7 μF

LED Drive Efficiency, fLED = 19.5 kHz, PSPWM enabled

30085819

Boost Converter Efficiency

30085825

Boost Maximum Output Current at VBOOST = 38V

30085827

Battery Current

30085828

Boost Converter Typical Waveforms

VBOOST = 38V, IOUT = 50 mA

30085829

Boost Line Transient Response

30085830

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LP8543

Typical Waveforms in PSPWM Mode, fLED = 4.2 kHz

30085831

Typical Waveforms in Normal PWM Mode, fLED = 4.2 kHz

30085832

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LP8543

Functional Overview

The LP8543 is a high-voltage LED driver for medium-sized

LCD backlight applications. It includes 38V boost converter,

7 current sink outputs for the backlight and an interface for

digital Ambient Light Sensor (ALS). LP8543 can be controlled

through SMBus or I2C serial interface or PWM input. Light-to-

frequency type ambient light sensor can be directly connected

to LP8543 and the sensor response vs. LED brightness curve

can be programmed in the on-chip EEPROM memory.

LP8543 differs from conventional LED drivers due to fol-

lowing advanced features.

1. PHASE SHIFT PWM FEATURE

LP8543 supports a state-of-the-art feature called Phase

Shift PWM (PSPWM). Key advantages of the PSPWM is

improved power efficiency when there is variation in the

forward voltages amongst the LED strings. Due to an

unmatched LED VF there is a random difference in each

string forward voltage. PSPWM optimizes the boost

converter output voltage by turning off LED outputs

periodically. The lower the brightness, the more strings

can be simultaneously off. When the strings with higher

forward voltages are turned off, the boost voltage is

automatically lowered thereby improving efficiency. The

second benefit of PSPWM control is that it will make the

boost and battery loading more constant. In other words,

the peak current needed from the battery is greatly

reduced beause not all LED outputs are simultaneously

on.

2. PROGRAMMABLE OUTPUT STRINGS

Programmability helps display manufacturers to fit

LP8543 to several sizes of displays. The number of

output strings in use is a parameter in EEPROM and can

be fixed during the manufacturing process of displays.

Based on the configuration the device will automatically

adjust the phase Shift PWM function for a given number

of output strings. LP8543 supports of minimum of 4

strings and a maximum of 7 strings. In this datasheet ,

strings 1 through 6 are classified as Display1, and string

7 is classified as Display2.

3. INDIVIDUALLY CONTROLLED LED STRING FOR

BACKSIDE DISPLAY BACKLIGHT

OUT7 string can be either used for main backlight or for

possible back side sub display. Separate control allows

dimming through I2C interface and reduces extra

components or ICs in display module.

4. LED FAULT DETECTION

LED fault detection enables higher yield in display

manufacturing process and also makes possible to

monitor backlight faults during normal operation. Fault

test detects both open circuit (string with unconnected or

open circuit LED) and short circuit of 2 or more shorted

LEDs. Single LED short can also be detected if the

amount of LEDs per string and/or the VF variation are

sufficiently low. Threshold levels are EEPROM

programmable. Fault information is available in the

status register and in the open drain active low FAULT

output.

5. LED PWM TEMPERATURE REGULATION

This feature will decrease the effect of high temperature

LED lifetime reduction. LP8543 reduces output PWM of

the LEDs at high temperatures and prevents overheating

of the device and LEDs. Temperature threshold can be

programmed to EEPROM.

6. AMBIENT LIGHT SENSOR INTERFACE WITH USER

PROGRAMMABLE CONTROL CURVE

Ambient light sensing reduces power consumption and it

allows natural backlight in any ambient light condition.

Programmability allows display manufacturer and even

end user to control sensor to backlight control loop. By

integrating this feature LP8543 reduces external

component count, wiring and complexity of the design.

LP8543 supports digital light-to-frequency type sensors.

Prescaler and compensation curve can be programmed

in to the EEPROM.

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LP8543

Brightness Control Methods

1. CURRENT CONTROL

The 8-bit LED current default value is read from

EEPROM when the chip is activated. Current value can

be used for fine tuning the backlight brightness between

panels. This current setting can be overridden by a

range is from 0 to 60 mA with 0.23 mA step. This fine

grained current control gives backlight manufacturer

possibility to adapt different LED bins in one product and

maintain the full PWM control range. There are separate

controls for both Display1 and Display2.

2. INTERNAL PWM CONTROL

The basic brightness control is register based 8-bit PWM

control. There is a piecewise linear transfer curve from

coefficients are stored in the EEPROM. This makes

possible to calibrate the 100% brightness and the

dimming behavior. LED PWM frequency is selectable

from 229 Hz to 19.5 kHz. In addition PSPWM can be

used.

3. EXTERNAL PWM CONTROL

An external PWM signal can be used to set the

brightness of the display. LP8543 measures the duty

cycle of this input signal to calculate the output PWM

value. Input PWM frequency can vary from 100 Hz to 25

kHz. Based on the configuration selected, this external

PWM control can linearly reduce the brightness from the

value set by the Brightness Register. This external PWM

control can also be used as the only control for LP8543.

In this case, when PWM input is permanently low, the

chip is turned off. When there is signal in PWM input, the

chip turns on and adjusts brightness according to PWM

signal duty cycle. In addition, PSPWM can also be used

in this mode.

4. AMBIENT LIGHT SENSING

External ambient light sensor can be used for controlling

the brightness of the LEDs. Light-to- Frequency type light

sensor can be connected to ALSI input in LP8543 for

ambient light compensation. Transfer curve coefficients

for response setting are stored in EEPROM. LP8543 has

an enable output, ALSO to activate the light sensor

(active high/low, programmed to EEPROM). Light sensor

supply voltage can be taken from the 5V regulator in

LP8543. Ambient light control is possible for Display1

(4-7 outputs).

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LP8543

Calibration

LP8543 has an internal EEPROM to store different control

parameters which allows calibrating the backlight brightness

at various brightness settings so that every display has ex-

actly the same brightness and several LP8543 circuits can be

used in the same display if needed.

Programming the EEPROM is easy. User needs to write the

data in the shadow RAM memory and give the EEPROM write

command. On-chip boost converter produces the needed

erase and program voltages, no external voltages other than

normal input voltage are required.

Calibration in backlight or display production can be done ac-

cording to the flowchart below

30085803

Energy Efficiency

The voltage across the LED drivers is constantly monitored

and boost voltage is adjusted to minimum sufficient voltage

when adaptive boost mode is selected. Inductive boost con-

verter maintains good efficiency over wide input and output

operating voltage ranges. The boost output has over voltage

protection limiting the maximum output to 38V. The boost is

internally compensated and the output voltage can be either

controlled with 5-bit register value or automatically adjusted

based on the LED driver voltages.

LP8543 has an internal 5V LDO with low current consump-

tion. The 5V LDO can supply 5 mA current for external devices

like ALS (Ambient Light Sensor). LDO is switched off in stand-

by mode. The internal LDO is used for powering internal

blocks as well; therefore the 470 nF CVLDO capacitor must be

used even if external load is not used.

Serial Communication

LP8543 supports two serial protocols: SMBus and I2C.

IF_SEL input is used to determine the selection. SMBus in-

terface is selected when IF_SEL is high and I2C is selected

when IF_SEL is low.

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LP8543

Block Diagram

30085874

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LP8543

LED Driver Control

BASIC OPERATION

Principle of the LED driver control is shown in the following

figure:

30085804

Principle of the LED Control Methods

LP8543 is designed to be flexible to support backlighting

needs for the main display as well as lighting needs of a sub

display (also for e.g. keyboard lighting or status LED) when

required. In addition, a variety of PWM options are supported

to drive the backlight LED strings. Various configurations that

are supported using a set of programmable internal registers

and EEPROM are described below. Both the register map

and the EEPROM memory map are listed at the end of this

datasheet.

OUTPUT GROUPING

LP8543 features a total of 7 strings (OUT1-OUT7), which can

be arranged into 2 groups (Display1 and Display2). Display1

refers to backlighting for main display and Display2 refers to

lighting for a sub display. Number of outputs used for Display1

can be defined using EEPROM register bits, as shown in the

table below. LP8543 supports a minimum of 4 strings and a

maximum of 7 strings for Display1. Outputs must be used in

order starting from OUT1. Unused outputs can be left open.

When needed OUT7 can be configured for Display2 and it has

its own current and PWM control registers for independent

control. EEPROM default factory setting is 6 outputs for Dis-

play1 and OUT7 for Display2.

TABLE 1. Output Configurations

OUTPUT_CONF[1:0] Outputs for

Display1

Outputs for

Display2

00 OUT1-OUT4 OUT7

01 OUT1-OUT5 OUT7

10 OUT1-OUT6 OUT7

11 OUT1-OUT7 -

LED CURRENT CONTROL

Two 8-bit EEPROM registers, Display1 current and Dis-

play2 current (addresses B0H and B1H) hold the default

LED string current for the Display1 and Display2 groups re-

spectively. The default values are read from EEPROM when

the chip is activated. When required the LED current can be

adjusted also in the registers Display1 and Display2 cur-

rent (addresses 05H and 06H). Use of this register is enabled

by setting bit 1 in Config2 register. Default value for <CUR-

RENT SEL> bit is 0, which means that current values in

EEPROM are used. Current control range is linear from 0 to

60 A with 0.23 mA step. Factory default current for Display1

and Display2 is 20 mA.

LED ON/OFF CONTROL

LED strings can be activated with 100% PWM by writing

<DRV[7:0]> bits high. All these controls are in Direct con-

trol register.

PWM CONTROL SELECTION

PWM control of the LED strings can be established through

4 combinations of user configurable options as shown in the

table below. <PM_MD> and <PWM_SEL> bits are part of

Config1 Register.

Default setting is external PWM input signal. Each of the op-

tion is explained in the following sections.

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LP8543

TABLE 2. PWM Control Selection

PWM_MD PWM_SEL PWM source

1 1 PWM input (Direct control)

0 1

PWM input pin (Duty cycle

based), default

1 0 Brightness register

0 0

PWM input pin (Duty cycle

based) and Brightness register

In addition Ambient light sensor (when used) and on-chip

temperature regulation also influence the output PWM con-

trol. This is described later.

A. Direct PWM Input Control

Display1 group can be directly controlled with external PWM

signal (bypassing all the PWM logic) by setting <PWM_MD>

and <PWM_SEL> bits high. Outputs will be active when the

PWM input pin is high, and when the input is low the outputs

will be off. Input PWM frequency can vary from 100 Hz to 25

kHz. Display2 is not controlled with this signal.

Note: In this mode, Ambient Light sensor and PSPWM

scheme do not influence the output PWM.

B. PWM Input Pin Control (Duty Cycle-based)

An external PWM signal can be used to set the brightness of

the Display1 group. LP8543 measures the duty cycle of this

input signal to calculate the output PWM value. Input PWM

frequency can vary from 100 Hz to 25 kHz. Output PWM fre-

quency is set by EEPROM registers.

Note: In this mode, Ambient Light compensation and PSPWM

scheme can be also used.

C. PWM Control Using Brightness Register

Generation of PWM for LED strings can be based on Bright-

ness register value. For Display1 group, this scheme is en-

abled when <PWM_SEL> bit is set to 0 and <PWM_MD> is

set to 1. Display2 group has the brightness register control

enabled by default. Two separate 8-bit registers Displ1

brightness and Displ2 brightness store the brightness val-

ues for Display1 and Display2 respectively. For Display1, this

8-bit brightness value from the register is converted to 10-bit

LED PWM value using a three-part piecewise linear transfer

curve as shown below. This makes it possible to calibrate the

100% brightness and the dimming behavior. The curve coef-

ficients are stored in the EEPROM and are user pro-

grammable if needed. The LED PWM frequency is set by

EEPROM register.

Note: In this mode, Ambient Light compensation and PSPWM

scheme can be also used.

30085821

Three-Segment Transfer Curve Example

D. PWM Pin and Register Control

In this mode, PWM control pin can linearly reduce the bright-

ness of Display1 from the value set by the Brightness Register

and Ambient Light sensor. Same controls can be used as in

brightness register based PWM control. Output PWM fre-

quency is set by EEPROM registers. This mode is compatible

with Intel DPST (Display Power Saving Technology).

STAND ALONE MODE

LP8543 can be set to operate in stand alone mode, where

LP8543 operates without I2C / SMBus and EN and PWM input

pins are the only controls for the device. To enable stand-

alone mode, EEPROM bit <EN_STANDALONE> must be set

to 1 in register B4h. In this mode PWM pin sets the brightness

and with EN pin the backlight can be turned on. When PWM

or EN input pin is permanently low, the chip is turned off. Turn

off time is typically 50 ms. When there is signal in PWM input

and EN is high, the chip turns on and adjusts brightness ac-

cording to PWM signal duty cycle. All settings needed for

operation like LED current, number of LEDs etc. are obtained

from EEPROM. If only one signal control is needed, the EN

and PWM pin can be tied together and PWM signal can be

connected to this. Stand alone mode is useful in applications

where I2C or SMBus control is not possible or available to use.

AMBIENT LIGHT COMPENSATION

LP8543 supports an external ambient light sensor to control

the backlight brightness (Display1) and its usage is controlled

with two bits in the Config2 register, namely <ALSO_EN>

and <ALSO_CALC_EN>. <ALSO_EN> bit controls enabling/

disabling of the sensor itself, and <ALSO_CALC_EN> bit de-

termines whether the ALS measurement data will be used by

an external processor (Host) or by LP8543’s internal control

logic to control the brightness.

If <ALSO_EN> bit is 1 the ALSO output pin is set high and the

input frequency measuring is enabled. Frequency is mea-

sured for 500 ms, and the result is divided with 10-bit

prescaler (defined in EEPROM), resulting in a 10-bit value.

This 10-bit result can be read from ALS MSB and ALS LSB

registers. ALS MSB register must be read first followed by

ALS LSB register. If ALS_CALC_EN bit is set to 0, then the

measurement data is not used by LP8543’s internal PWM

logic but left for the host to adjust the brightness.

On the other hand if the ALS_CALC_EN bit is set to 1, ALS

measurement result will control backlight brightness in all but

direct external PWM control mode. The measured ALS value

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LP8543

is converted to PWM value using a three segment linear

curve. The calculated PWM value is used as a multiplier for

the LED PWM value obtained from brightness register, PWM

input pin or combination of both depending which mode is

selected. The conversion curve parameters are stored in

EEPROM memory. Conversion curve is similar as in PWM

control.

Smoothing filter is used to prevent rapid changes. Smoothing

filter has EEPROM programmable slopes from 0 to 2s. The

slope defines the time it takes to change brightness from one

value to next. Slope control can be also used to smooth

changes to backlight brightness caused by other PWM con-

trols (brightness register or external PWM input).

TABLE 3. Slope Selections

SLOPE_SEL[1:0] Slope

00 130 ms

01 0.5s

10 1.0s

11 2s

ALSO output can be used as GPO if not used for ALS control.

ALSO pin state is then controlled with <ALSO_EN> register

bit.

PHASE SHIFT PWM (PSPWM)

PSPWM improves the system efficiency by optimizing the

boost converter voltage on a cycle by cycle basis instead of

maintaining a constant voltage based on the highest VF string.

PSPWM scheme can be used for Display1 group. Phase shift

PWM control principle is illustrated in the picture below using

an example of 6 string implementation and 41.7% brightness

setting. In a 6-string implementation, each of the string sup-

ports a maximum of 16.67% (1/6) of the total backlight bright-

ness. The brightness set value in this example is 41.7%.

Hence two strings are fully on (2 x 16.67% = 33.33%) and one

string is 50% on (0.5 x 16.67% = 8.34%). This pattern of two

100% and one 50% strings is then cycled through all 6 output

strings. After 6 cycles the brightness value is changed to

83.33%, resulting in 5 LEDs fully on (5 x 16.67%).

30085805

Principle of the PSPWM Operation

Phase shift frequency can either be the same as the PWM

frequency or a lower frequency can be selected with

<PHASE_SHIFT_FREQ[1:0]> EEPROM bits. At highest 19.5

kHz PSPWM frequency, the boost will use a constant voltage

based on the highest VF string because of timing constraints

of the high PWM frequency. PSPWM is enabled by default,

but it can be disabled by setting <DISABLE_PS> EEPROM

bit to 1.

Two PSPWM modes are available. PSPWM mode is selected

with <PWM_MODE> EEPROM bit. Difference between

modes is in the PWM frequencies available. PWM and PSP-

WM frequency settings are shown in Table 4.

Number of strings simultaneously on in PSPWM mode with

different PWM values and different output configurations is

shown in the following diagram.

30085806

Number of Simultaneously Active Strings

17 www.ti.com

LP8543

TABLE 4. PSPWM Frequency Selection in EEPROM Registers (N = number of strings used)

PWM_MODE = 0 PWM_MODE = 1

PWM_FREQ[2:0] +

PSPWM_FREQ[1:0]

PWM Frequency

(Hz)

Shift Frequency

(Hz)

Output Frequency

(Hz)

Output Frequency

(Hz)

Shift Frequency

(Hz)

00000 992 992 992/N 229 229 x N

00001 992 496 496/N 305 305 x N

00010 992 248 248/N 381 381 x N

00011 992 124 124/N 458 458 x N

00100 1526 1526 1526/N 534 534 x N

00101 1526 763 763/N 610 610 x N

00110 1526 382 382/N 687 687 x N

00111 1526 191 191/N 763 763 x N

01000 1983 1983 1983/N 839 839 x N

01001 1983 993 993/N 916 916 x N

01010 1983 496 496/N 992 992 x N

01011 1983 248 248/N 1068 1068 x N

01100 2441 2441 2441/N 1144 1144 x N

01101 2441 1221 1221/N 1221 1221 x N

01110 2441 610 610/N 1297 1297 x N

01111 2441 305 305/N 1373 1373 x N

10000 2974 2974 2974/N 1450 1450 x N

10001 2974 1487 1487/N 1526 1526 x N

10010 2974 744 744/N 1602 1602 x N

10011 2974 372 372/N 1678 1678 x N

10100 3965 3965 3965/N 1755 1755 x N

10101 3965 1983 1983/N 1831 1831 x N

10110 3965 991 991/N 1908 1908 x N

10111 3965 496 496/N 1983 1983 x N

11000 4883 4883 4883/N 2060 2060 x N

11001 4883 2441 2441/N 2671 2671 x N

11010 4883 1221 1221/N 3203 3203 x N

11011 4883 610 610/N 3737 3737 x N

11100 19531 19531 19531/N 4270 4270 x N

11101 19531 9766 9766/N 4808 4808 x N

11110 19531 4883 4883/N 9766 9766 x N

11111 19531 2441 2441/N 19531 19531 x N

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LP8543

TABLE 5. PWM Frequencies with Phase Shift Disabled

PWM_MODE = 0 PWM_MODE = 1

PWM_FREQ[2:0] +

PSPWM_FREQ[1:0]

PWM Frequency (Hz) Output Frequency (Hz)

00000 992 229

00001 992 305

00010 992 381

00011 992 458

00100 1526 534

00101 1526 610

00110 1526 687

00111 1526 763

01000 1983 839

01001 1983 916

01010 1983 992

01011 1983 1068

01100 2441 1144

01101 2441 1221

01110 2441 1297

01111 2441 1373

10000 2974 1450

10001 2974 1526

10010 2974 1602

10011 2974 1678

10100 3965 1755

10101 3965 1831

10110 3965 1908

10111 3965 1983

11000 4883 2060

11001 4883 2671

11010 4883 3203

11011 4883 3737

11100 19531 4270

11101 19531 4808

11110 19531 9766

11111 19531 19531

19 www.ti.com

LP8543

Device Thermal Regulation

LP8543 has an internal temperature sensor which can be

used to measure the junction temperature of the device and

protect the device from overheating. During thermal regula-

tion, LED PWM is reduced by 4% of full scale per °C whenever

the temperature threshold is reached. I.e., with 100% PWM

value the PWM goes to 0% 25°C above threshold tempera-

ture. With lower PWM start value 0% is reached earlier.

Temperature regulation is enabled automatically when the

chip is enabled. 11-bit temperature value can be read from

Temp MSB and Temp LSB registers, MSB should be read

first. Temperature limit can be programmed in EEPROM as

shown in the following table.

TABLE 6. Over Temperature Limit Settings

TEMP_LIM[1:0] Over Temperature Limit (ºC)

00 100

01 110

10 120

11 130

30085823

Internal Temperature Sensor Readings

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LP8543

EEPROM

EEPROM memory stores various parameters for chip control.

The 256 bit EEPROM memory is organized as 32 x 8 bits. The

EEPROM structure consists of a SRAM front end and the

Non-volatile memory (NVM). SRAM data can be read and

written through the serial interface. To erase and write NVM,

separate commands need to be sent. Erase and Write volt-

ages are generated on-chip, no other voltages than normal

input voltage are required. A complete EEPROM memory

map is shown in the chapter LP8543 EEPROM Memory Map.

EEPROM structure is described in the figure below. User has

read and write access to SRAM part of the EEPROM directly

through I2C / SMBus when PWM calculation is not enabled;

i.e., <BL_CTL> = 0 and external PWM pin = low. To see

whether the EEPROM can be accessed user can read

<EE_READY> bit. ALS and brightness coefficient curves (ad-

dress A0h – Afh) and empty EEPROM cells (address B4h –

BBh) have only NVM and SRAM. Other EEPROM cells have

also EEPROM registers. For the cells which have also EEP-

ROM registers, the changes made to SRAM does not take

effect until update command is sent. This is done by setting

EE_UPDATE and EE_READ bits to 1. After an update, these

bits must be set back to 0. For EEPROM bits which do not

have registers, changes take effect immediately.

At startup the values in NVM part of the EEPROM is loaded

to SRAM and to EEPROM registers. User can also load val-

ues from NVM to SRAM and EEPROM registers by writing

EE_READ to 1.

To write SRAM values to NVM user needs to first erase EEP-

ROM and the program it. This is done by first writing

EE_ERASE to 1 and then 0. At this point NVM is erased. To

burn new values to NVM, user needs to write EE_PROG to 1

and then 0. The LP8543 generates the needed erase and

write voltage from boost output voltage.

30085839

EEPROM Memory Control and Usage Principle

21 www.ti.com

LP8543

Boost Converter

OPERATION

The LP8543 boost DC/DC converter generates a 10…38V

supply voltage for the LEDs from 5.5…22V input voltage. The

output voltage is controlled with a 5-bit register in 1V steps.

The converter is a magnetic switching PWM mode DC/DC

converter with a current limit. The topology of the magnetic

boost converter is called CPM (current programmed mode)

control, where the inductor current is measured and con-

trolled with the feedback. Switching frequency is selectable

between 625 kHz and 1.25 MHz with EEPROM bit

<BOOST_FREQ>. Boost is enabled with <EN_BOOST> bit.

User can program the output voltage of the boost converter

or use adaptive mode where boost output voltage is adjusted

automatically based on LED driver saturation. In adaptive

mode the boost output voltage control steps are 0.25V. En-

abling the adaptive mode is done with <BOOST_AUTO> bit

in Boost Control register. If boost is started with adaptive

mode enabled (default) then the initial voltage value is defined

with EEPROM bits at address 29H in order to eliminate long

iteration time when the chip is started. If adaptive mode is

enabled after boost startup, then the boost will use register

07H values as initial voltage value. The output voltage control

changes the resistor divider in the feedback loop. The follow-

ing figure shows the boost topology with the protection cir-

cuitry.

30085840

PROTECTION

Four different protection schemes are implemented:

1. Over-voltage protection limit changes dynamically based

on output voltage setting

—Over-voltage protection limit changes dynamically

based on output voltage setting.

—Keeps the output below breakdown voltage.

—Prevents boost operation if battery voltage is much

higher than desired output.

2. SW current limiting, limits the maximum inductor current.

3. Over-current protection enables fault flag and shuts

down boost converter in over-current condition.

4. Duty cycle limiting.

MANUAL OUTPUT VOLTAGE CONTROL

User can control the boost output voltage with Boost_out-

put (07H) register when adaptive mode is disabled; i.e.,

<BOOST_AUTO> = 0.

TABLE 7. Boost Output Voltage Controls

VPROG[4:0] Voltage (typical)

Bin Dec Volts

00000 0 10

00001 1 11

00010 2 12

00011 3 13

00100 4 14

... ... ...

11011 27 37

11100 28 38

ADAPTIVE BOOST CONTROL

Adaptive boost control function adjusts the boost voltage to

the minimum sufficient voltage for proper LED driver opera-

tion. When PSPWM is used the output voltage can be adjust-

ed for every phase shift step separately except in 19.5 kHz

PSPWM mode due to timing constraints. To enable PSPWM

to each phase, the <BOOST_MODE> EEPROM bit must be

0. This enables power saving when strings have mismatch in

VF voltages. The correct voltage for each string is stored and

used in predicting when the boost has to start increasing volt-

age for the next step. The boost setup time can be defined

with two EEPROM bits. Principle of the boost voltage adjust-

ment with PSPWM is illustrated below. If higher PWM value

is used then more strings are on at the same time, and voltage

is adjusted based on highest VF on simultaneously active

strings.

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LP8543

30085841

Boost Adaptive Voltage Control for 5–String PSPWM

When adaptive boost mode is selected the voltages across

the LED drivers are constantly monitored. There are three

voltage thresholds used, Low, Mid and High. Low and High

thresholds are adjustable with 3 EEPROM bits. Low threshold

range is from 0.5V to 2.25V and High threshold range is from

3 to 10V. Mid threshold is set 0.5V above Low threshold.

Threshold levels are listed in the table below. Adjustability is

provided to enable adaptation to different conditions. If there

is a lot of variation between LED string VF, then higher thresh-

old levels must be used to avoid false fault indications. If there

is low variation between LED string VF, then lower thresholds

are recommended to maintain good efficiency. Fault detec-

tion chapter describes how these thresholds are used also for

fault detection.

TABLE 8. LED Voltage Comparator Thresholds

EEPROM bits Threshold (V)

LED_FAULT_THR[5:3]

(HIGH comparator)

DRV_HEADR_CTRL[2:0]

(LOW comparator)

Low High Mid

000 0.50 3

Low + 0.5V

001 0.75 4

010 1.00 5

011 1.25 6

100 1.50 7

101 1.75 8

110 2.00 9

111 2.25 10

If only one string is on at a time (Brightness value lower than

100% divided by number of strings) the voltage for each string

is adjusted so that the voltage across the driver will fall be-

tween Low and Mid threshold. If more strings are on at the

same time (high PWM value, or PSPWM not used) the situ-

ation looks like in the following diagram. In this diagram 6

outputs are on at the same time. In normal operation voltages

across all LED driver outputs are between high and low

threshold.

30085842

Normal Operation, High PWM Value

If one LED driver voltage is below Low, boost voltage will be

increased. This is seen in the following figure.

30085843

Boost voltage too Low

If all driver voltages are above Mid threshold (or any of the

voltages in PSPWM adaptation mode and with low PWM val-

ue), boost voltage will be lowered. Decision is always based

on number of strings active at the same time. In the illustra-

tions 6 outputs are active, which basically means close to

100% PWM value with PSPWM.

30085844

Boost voltage too High

23 www.ti.com

LP8543

Fault Detection

LP8543 has fault detection for LED fault, low-battery voltage,

overcurrent and thermal shutdown. The open drain output pin

(FAULT) can be used to indicate occurred fault. The cause

for the fault can be read from status register. Refreshing the

<BL_CTL> bit high will reset the fault register and fault pin

state.

LED FAULT DETECTION

There are two methods of detecting the LED fault. First

method is based on measuring the voltage on LED driver pins

(analog fault detection) and another is based on adaptive

boost voltage hopping between strings (digital fault detec-

tion). The used fault detection mode is selected in EEPROM

as well as the threshold levels. <FAULT_SEL[1:0]> bits se-

lects the used mode as follows:

TABLE 9. LED Fault Mode Selection

FAULT_SEL[1:0] Fault mode

00 No fault detection

01 Analog fault detection based on

LED driver voltage

10 Digital fault detection based on

boost voltage hopping

11 Both analog and digital fault

detection

Two fault detection methods are used to detect faults in dif-

ferent conditions. Analog detection works better with high

PWM values (in PSPWM mode) where many strings are ac-

tive at a same time. It does not work when only one string is

active at a time, because it is based on comparing driver volt-

ages on strings active simultaneously. Digital fault detection

is used to complement this case.

Digital fault detection works better with low PWM values,

where not all strings are on at the same time. Digital short

detection works only with cases where one string is active at

the same time.

ANALOG FAULT DETECTION

When analog fault detection mode is selected, the voltages

across the LED drivers are constantly monitored. The same

threshold levels (Low, Mid and High) are used for fault detec-

tion to adjust the boost voltage.

If one of the LED strings has an open fault (LED driver output

pin has no contact to LED string), the output pin voltage drops

to 0V. When this happens the boost voltage will be adjusted

higher to get enough headroom, but at some point the voltage

for all other strings will rise over the high threshold. In this

case the LP8543 detects open fault, and adjusts the boost

voltage based on other LED strings needs, i.e., the faulty LED

string voltage is not used anymore for adjusting boost output

voltage. If the LED driver output pin is shorted to GND the

fault detection works exactly the same. This situation with 6

LEDs active at the same time is illustrated in the following

diagram:

30085845

Open Fault

If one or more LEDs are shorted, this causes the voltage to

rise in this LED driver output pin above the high threshold.

This causes short fault detection as seen in the following fig-

ure:

30085846

Short Fault

DIGITAL FAULT DETECTION

With digital fault detection the voltage hopping between LED

strings is monitored in PSPWM mode. In normal PWM mode

or with high PWM values with PSPWM mode this does not

apply.

If there’s open in one of the LED strings, the LED driver output

pin will drop to 0V. When this happens the boost will try to

increase the voltage to get enough headroom for the driver.

When the voltage for one string reaches maximum voltage

(38V) and the difference between consecutive LED strings is

higher than set threshold level an open LED fault is detected.

If all voltages are close to 38V then the threshold condition is

not met and no fault is detected. If the LED output is shorted

to GND it will be detected same way. Open fault detection is

seen in the following figure:

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LP8543

30085847

Digital Open Fault Detection

If there is one or more LEDs shorted in one string, the boost

will drop the voltage for this string. When the difference be-

tween consecutive LED strings is higher than set threshold

level a short LED fault is detected. This is described in the

following figure:

30085848

Digital Short Fault Detection

Threshold level is programmed to EEPROM as shown in the

following table. Threshold level adjustability is provided to al-

low adaptation to different LED VF used in the application.

TABLE 10. Digital LED Fault Detection Thresholds

DIG_COMP[1:0] Threshold Voltage (V)

00 3

01 5

10 7

11 9

When Fault is detected the FAULT pin will be pulled down

(open drain output), and corresponding status register bit is

set. To clear the fault user must read the status register.

Note: LED fault output signal is generated only once for cer-

tain fault type. If, for example, open fault occurs, new open

fault does not cause the FAULT pin to be pulled down uless

chip is reset by setting EN pin low and high again. The faults

will be seen in the register however. If LED fault is detected,

the string which created the fault is no longer used for adjust-

ing the boost voltage. Otherwise the LP8543 operates as

normally.

Note: Due to the nature of fault detection it is possible to gen-

erate false faults during startup etc. conditions. Therefore

when fault is detected it is recommended to read the fault/

status register twice to make sure that the first fault is real. If

the second reading gives the same result then the fault is real.

UNDER-VOLTAGE DETECTION

LP8543 has detection for too low VIN voltage. Threshold level

for the voltage is set with EEPROM register bits as seen in

the following table:

TABLE 11. Under-Voltage Detection Thresholds

UVLO_THR Threshold (V)

0 6

1 3

Under voltage detection is always on. When under voltage is

detected the LED outputs and boost will shutdown, Fault pin

will be pulled down (open drain output) and corresponding

fault bit is set in status register. Fault can be reset by reading

the status register. LEDs and boost will start again when the

voltage has increased above the threshold level. Hysteresis

is implemented to threshold level to avoid continuous trigger-

ing of fault when threshold is reached.

Note: Due to the nature of fault detection it is possible to gen-

erate false faults during startup etc. conditions. Therefore

when fault is detected it is recommended to read the fault/

status register twice to make sure that the first fault is real. If

the second reading gives the same result then the fault is real.

OVER-CURRENT DETECTION

LP8543 has detection for too high loading on the boost con-

verter. When over current fault is detected the LP8543 will

shut down and set the fault flag.

THERMAL SHUTDOWN

If the LP8543 reaches thermal shutdown temperature

(150°C) the LED outputs and boost will shut down to protect

it from damage. Also the fault pin will be pulled down to indi-

cate the fault state. Device will activate again when temper-

ature drops below 130°C.

25 www.ti.com

LP8543

SMBus/I2C Compatible Serial Bus

Interface

INTERFACE BUS OVERVIEW

The SMBus/I2C-compatible synchronous serial interface pro-

vides access to the programmable functions and registers on

the device. This protocol uses a two-wire interface for bidi-

rectional communications between the IC's connected to the

bus. The two interface lines are the Serial Data Line (SDA),

and the Serial Clock Line (SCL / SCLK). These lines should

be connected to a positive supply, via a pull-up resistor and

remain HIGH even when the bus is idle.

Every device on the bus is assigned a unique address and

acts as either a Master or a Slave depending on whether it

generates or receives the serial clock (SCLK). LP8543 is al-

ways a slave device.

DATA TRANSACTIONS

One data bit is transferred during each clock pulse. Data is

sampled during the high state of the serial clock (SCL). Con-

sequently, throughout the clock’s high period, the data should

remain stable. Any changes on the SDA line during the high

state of the SCLK and in the middle of a transaction, aborts

the current transaction. New data should be sent during the

low SCLK state. This protocol permits a single data line to

transfer both command/control information and data using the

synchronous serial clock.

30085849

Bit Transfer

Each data transaction is composed of a Start Condition, a

number of byte transfers (set by the software) and a Stop

Condition to terminate the transaction. Every byte written to

the SDA bus must be 8 bits long and is transferred with the

most significant bit first. After each byte, an Acknowledge sig-

nal must follow. The following sections provide further details

of this process.

30085820

Start and Stop

The Master device on the bus always generates the Start and

Stop Conditions (control codes). After a Start Condition is

generated, the bus is considered busy and it retains this sta-

tus until a certain time after a Stop Condition is generated. A

high-to-low transition of the data line (SDA) while the clock

(SCLK) is high indicates a Start Condition. A low-to-high tran-

sition of the SDA line while the SCLK is high indicates a Stop

Condition.

30085850

Start and Stop Conditions

In addition to the first Start Condition, a repeated Start Con-

dition can be generated in the middle of a transaction. This

allows another device to be accessed, or a register read cycle.

ACKNOWLEDGE CYCLE

The Acknowledge Cycle consists of two signals: the acknowl-

edge clock pulse the master sends with each byte transferred,

and the acknowledge signal sent by the receiving device.

The master generates the acknowledge clock pulse on the

ninth clock pulse of the byte transfer. The transmitter releases

the SDA line (permits it to go high) to allow the receiver to

send the acknowledge signal. The receiver must pull down

the SDA line during the acknowledge clock pulse and ensure

that SDA remains low during the high period of the clock

pulse, thus signaling the correct reception of the last data byte

and its readiness to receive the next byte.

“ACKNOWLEDGE AFTER EVERY BYTE” RULE

The master generates an acknowledge clock pulse after each

byte transfer. The receiver sends an acknowledge signal after

every byte received.

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LP8543

There is one exception to the “acknowledge after every byte”

rule. When the master is the receiver, it must indicate to the

transmitter an end of data by not-acknowledging (“negative

acknowledge”) the last byte clocked out of the slave. This

“negative acknowledge” still includes the acknowledge clock

pulse (generated by the master), but the SDA line is not pulled

down.

ADDRESSING TRANSFER FORMATS

Each device on the bus has a unique slave address. The

LP8543 operates as a slave device with the 7-bit address

combined with data direction bit. Slave address is pin-se-

lectable as follows:

TABLE 12. Address Selection

ADR Slave Address

Write (8 bits)

Slave Address Read

(8 bits)

01011000 (58H)

01011010 (5AH)

01011001 (59H)

01011011 (5BH)

Before any data is transmitted, the master transmits the ad-

dress of the slave being addressed. The slave device should

send an acknowledge signal on the SDA line, once it recog-

nizes its address.

The slave address is the first seven bits after a Start Condi-

tion. The direction of the data transfer (R/W) depends on the

bit sent after the slave address — the eighth bit.

When the slave address is sent, each device in the system

compares this slave address with its own. If there is a match,

the device considers itself addressed and sends an acknowl-

edge signal. Depending upon the state of the R/W bit (1:read,

0:write), the device acts as a transmitter or a receiver.

I2C Chip Address

30085851

Control Register Write Cycle

•Master device generates start condition.

•Master device sends slave address (7 bits) and the data

direction bit (r/w = 0).

•Slave device sends acknowledge signal if the slave

address is correct.

•Master sends control register address (8 bits).

•Slave sends acknowledge signal.

•Master sends data byte to be written to the addressed

•Slave sends acknowledge signal.

•If master will send further data bytes the control register

address will be incremented by one after acknowledge

signal.

•Write cycle ends when the master creates stop condition.

Control Register Read Cycle

•Master device generates a start condition.

•Master device sends slave address (7 bits) and the data

direction bit (r/w = 0).

•Slave device sends acknowledge signal if the slave

address is correct.

•Master sends control register address (8 bits).

•Slave sends acknowledge signal.

•Master device generates repeated start condition.

•Master sends the slave address (7 bits) and the data

direction bit (r/w = 1).

•Slave sends acknowledge signal if the slave address is

correct.

•Slave sends data byte from addressed register.

•If the master device sends acknowledge signal, the control

sends data byte from addressed register.

•Read cycle ends when the master does not generate

acknowledge signal after data byte and generates stop

condition.

TABLE 13. Data Read and Write Cycles

Address Mode

Data Read

<Slave Address><r/w = 0>[Ack]

<Register Addr.>[Ack]

<Slave Address><r/w = 1>[Ack]

[Register Data]<Ack or NAck>

… additional reads from subsequent

Data Write

<Slave Address><r/w=’0’>[Ack]

<Register Addr.>[Ack]

<Register Data>[Ack]

… additional writes to subsequent

<>Data from master [ ] Data from slave

27 www.ti.com

LP8543

30085894

30085895

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LP8543

Recommended External Components

Inductor Selection

A 15 µH shielded inductor is suggested for LP8543 boost

converter. Inductor maximum current can be calculated from

the equations below.

• IRIPPLE: Average to peak inductor current

• IOUTMAX: Maximum load current

• VIN: Maximum input voltage in application

• L: Min inductor value including worst case tolerances

• f: Minimum switching frequency

• VOUT: Output voltage

Example using above equations:

•VIN = 12V

•VOUT = 38V

•IOUT = 400 mA

•L = 15 µH − 20% = 12 µH

•f = 1.25 MHz

•ISAT = 1.6A

As a result the inductor should be selected according to the

ISAT. A more conservative and recommended approach is to

choose an inductor that has a saturation current rating greater

than the maximum current limit of 0.9...2.5A (programmed to

EEPROM). Maximum current limit needed for the application

can be approximated with calculations above. A 15 μH induc-

tor with a saturation current rating of 2.5A is recommended

for most applications. The inductor’s resistance should be

less than 300 mΩ for good efficiency. For high efficiency

choose an inductor with high frequency core material such as

ferrite to reduce core losses. To minimize radiated noise, use

shielded core inductor. Inductor should be placed as close to

the SW pin and the IC as possible. Special care should be

used when designing the PCB layout to minimize radiated

noise and to get good performance from the boost converter.

OUTPUT CAPACITOR

A ceramic capacitor with 50V voltage rating or higher is rec-

ommended for the output capacitor. The DC-bias effect can

reduce the effective capacitance by up to 80%, which needs

to be considered in capacitance value selection. For light

loads (<100 mA) 4.7 µF capacitor is sufficient. For maximum

output voltage/current 10 µF capacitor (4 uF effective capac-

itance @ 38V) is recommended to reduce the output ripple.

Small 33 pF capacitor is recommended to use in parallel with

the output capacitor to suppress high frequency noise.

LDO CAPACITOR

A 470 nF ceramic capacitor with 10V voltage rating is recom-

mended for the LDO capacitor.

OUTPUT DIODE

A schottky diode should be used for the output diode. Peak

repetitive current should be greater than inductor peak current

(0.9...2.5A) to ensure reliable operation. Average current rat-

ing should be greater than the maximum output current.

Schottky diodes with a low forward drop and fast switching

speeds are ideal for increasing efficiency in portable applica-

tions. Choose a reverse breakdown voltage of the Schottky

diode significantly larger (~60V) than the output voltage. Do

not use ordinary rectifier diodes, since slow switching speeds

and long recovery times cause the efficiency and the load

regulation to suffer.

AMBIENT LIGHT SENSOR

LP8543 uses light-to-frequency type ambient light sensor.

Suitable frequency range for ALS is 200 Hz to 2 MHz.

29 www.ti.com

LP8543

LP8543 Register Map

ADDR REGISTER D7 D6 D5 D4 D3 D2 D1 D0 DEFAULT

00H Display1 PWM DISP1_PWM[7:0] 1111 1111

01H Config1 PWM_MD PWM_SEL BL_CTL 0000 0000

02H Status 2_CH_SD 1_CH_SD BL_STAT OV_CURR THRM_SHDN FAULT 0000 0000

03H Identification LED_PANEL MFG[3:0] REV[2:0] 1111 1001

04H Output Control OUT[7:1] 0000 0000

05H Display1 Current DISP1_CURRENT[7:0] 0000 0000

06H Display2 Current DISP2_CURRENT[7:0] 0000 0000

07H Boost Control BOOST_AUTO EN_BOOST VPROG[4:0] 0110 0000

08H Display2 PWM DISP2_PWM[7:0] 0000 0000

09H Config2 CURRENT_SEL ALS_SEL ALS_CALC_EN ALS_EN 0000 0000

0AH ALS MSB ALS[9:2] 0000 0000

0BH ALS LSB ALS[1:0] 0000 0000

0CH Fault DISP2_FAULT DISP1_FAULT LED_OPEN LED_SHORT UVLO 0000 0000

0DH TEMP MSB TEMP[10:3] 0000 0000

0EH TEMP LSB TEMP[2:0] 0000 0000

72H EEPROM_control EE_READY NSTBY EE_UPDATE EE_ERASE EE_PROG EE_READ 0000 0000

www.ti.com 30

LP8543

LP8543 EEPROM Memory Map

ADDR D7 D6 D5 D4 D3 D2 D1 D0 DEFAULT

A0H ALS A1[7:0] 3DH

A1H ALS B1[7:0] 0AH

A2H ALS THR[7:0] FFH

A3H ALS A2[7:0] 00H

A4H ALS B2[7:0] FFH

A5H ALS THR2[7:0] FFH

A6H ALS A3[7:0] 00H

A7H ALS B3[7:0] FFH

A8H PWM A1[7:0] 40H

A9H PWM B1[7:0] 00H

AAH PWM THR1[7:0] FFH

ABH PWM A2[7:0] 00H

ACH PWM B2[7:0] FFH

ADH PWM THR2[7:0] FFH

AEH PWM A3[7:0] 00H

AFH PWM B3[7:0] FFH

B0H DISP1_CURRENT[7:0] 62H

B1H DISP2_CURRENT[7:0] 62H

B2H SLOPE_SEL[1:0] OUTPUT_CONF[1:0] ALS_EN ALSO_POLARITY BOOST_FREQ UVLO_THR 21H

B3H EN_SLOPE reserved TEMP_LIM[1:0] FAULT_SEL[1:0] EN_DISP2_MON DIS_TEMP_CALC A4H

B4H reserved EN_STANDALONE reserved EN_AUTOLOAD BOOST_MODE DISABLE_PS FILTER_TIME 45H

B5H PWM_MODE BOOST_UP[1:0] PWM_FREQ[2:0] PSPWM_FREQ[1:0] BCH

B6H Reserved 00H

B7H Reserved 00H

B8H Reserved 00H

B9H Reserved 00H

BAH Reserved 00H

BBH Reserved 00H

BCH DIG_COMP[1:0] LED_FAULT_THR[2:0] DRV_HEADR_CTRL[2:0] 90H

BDH Reserved IMAX_SEL[1:0] VPROG[4:0] 7CH

BEH ALS_PRESCALE[9:2] 7AH

BFH ALS_PRESCALE[1:0] Reserved Reserved Reserved Reserved Reserved Reserved 00H

31 www.ti.com

LP8543

www.ti.com 32

LP8543

Physical Dimensions inches (millimeters) unless otherwise noted

SQA24A: LLP-24, 0.5mm pitch, no pullback

33 www.ti.com

LP8543

Notes

LP8543 SMBus/I2C Controlled WLED Driver for Medium-Sized LCD Backlight

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