Lcd Driver Webinar Final File 2011

8/3/2019 Lcd Driver Webinar Final File 2011

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NXP LCD Drivers Webinar

Alvin Tan Senior Regional Marketing Manager, South Asia Pacific

2011


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NXP LCD Driver Portfolio

LCD Segment Drivers

LCD Character Drivers

LCD Graphic Drivers

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LCD Driver Key Values

Segment Driver

High segment count

Support for high segment count with one single device

for cost-optimized solutions

60 x 4, 80 x 4, 160 x 4, 60 x 8,

Automotive Qualification AEC-Q100 compliant automotive qualification ensuring

highest reliability. Non AEC-Q100 parts benefit from experience gained

Character Driver

Icon Row Separate icon row for versatile usage

Graphic Drivers

Niche resolution Resolution that not common in the market

34 x 128, 65 x 133, 80 x 128

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LCD segment driver

I2C Bus

sequencer

bias voltage generator

RAM

controllogic

backplanedriver

segmentdriver

Features

Wide range of segment outputs

On-chip RAM

Low power consumption

No external components

Wide power supply range

On-chip LCD bias voltage generation

LCD Segment DriversPortfolio Overview

Key productsPCF85162 4 x 32 segments

PCF85176 4 x 40 segments




PCF8537 8 x 44 segmentsPCA9620 8 x 60 segments

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LCD Segment DriversSelection Matrix

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NXP LCD Driver Portfolio

LCD Segment Drivers


LCD Graphic Drivers

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LCD character driver

I2C Bus /4/8bit parallel

characterRAM

controllogic

characterROM

displayRAM

sequencer


rowdriver

columndriver

Features

On-chip character generator

On-chip temperature compensation

On-chip character ROM and RAM


Minimum of external components

On-chip LCD bias voltage generation

Cursor support

Key products

PCF2113 2 line by 12 characters + 120 icons

PCF2119 2 line by 16 characters + 160 icons

LCD Character DriversPortfolio Overview

ChargePump

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CWG LCD Character DriversSelection Matrix

Note: 240 characters in ROM; 16 characters in RAM; character size: 5 x 8 dots or 5 x 7 dots + cursor

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LCD Driver Portfolio

LCD Segment Drivers


LCD Graphic Drivers

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Key productsPCF8531 34 x 128 small 4 x 20 chars of text, full graphic

PCF8811 80 x 128 large universal display

Features

Wide range of mux rates to optimizepower and display size

On-chip generation of LCD bias voltages

Low number of external components


Temperature compensation

LCD graphic driver

Serial /parallel /

I2C Interface

controllogic

displayRAM

sequencer


rowdriver

columndriver

LCD Graphic DriversPortfolio Overview

ChargePump

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PCF8534A automotive 6x40 LCD Driver with I2C Interface

High-Lights

240 segment drive

Simple mux 1:4

AEC-Q100 automotive compliant

Key Features

Bias voltage generation

Wide power supply range from 1.8V

to 5.5V Wide VLCD range from 2.5V to

6.5V

I2C interface ( 400kHz )

Cascadable up to 3,840 segments

LQFP80, U for COB application

Applications

Dash boards

Climate Control

Industrial Displays

PCA8534A

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PCF85132 Mux 1:4 COG 640-Segment DriverIn addition second set of

BackplanesHigh-Lights

640 segment drive

Simple mux 1:4

Programmable frame frequency

Duplicated Backplane pads on each side of the chip

AEC-Q100 automotive compliant is also available

Key Features

Bias voltage generation Wide power supply range from 1.8V to 5.5V

Wide VLCD range from 2.5V to 6.5V

I2C interface ( 400kHz )

Cascadalibity

Die with gold bumps for COG applications

Applications

Dash boards

Climate Control

Industrial Displays

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PCF85132 160 x 4 LCD Driver with I2C Interface

Example: Workout Equipment Application

488 segments driven with one single IC

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LCD Driver Rationale

Package aspects: LCD driver for >64 segments requires >16 outputs:

adding LCD function to C asks for high pin count package (cost not proportional)

C with small LCD driver on board is cost effective

Voltage requirements: Vop for LCD typical 3 9V, depending of multiplex rate and type

of liquid crystal; this is in hard contrast to modern C with typical VDD of 3.3 or 2.5V

Power aspects: in portable equipment the C is put to power down, sleep or hibernation

mode, but the display has to stay on to indicate status; with an external LCD driver this

can be done without any bus interference problems.

Module integration: With an external LCD driver, display and control functions can be

physically placed on the optimal location e.g LCD driver (module) on front panel, C on

main board. LCD module can be engineered in a compact way including also backlight,

protection glass, etc.

Microcontroller with integrated LCD Driver vs. MCU with external LCD Driver

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TN in Operation II

a b

incident light

segment: transparent opaque

polarizer, direction ofpolarization

cell glass

molecule orientationsegment electrode, directionof surface treatment

Glass thickness: 0.55, 0.7, 1.1mmLiquid Crystal: 6m, 9 mPolarizer foil: typical 0.1mmITO: 0.1 m

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Different Cell Types I

4 different LCD-cell types are popular:

TN: Twisted Nematic, 900 twistused for low mux-rates up to 1:8

STN: Super Twisted Nematic, 2700

twistused for high mux-rates 1:8 and up

DSTN: Double STN, the twist is reversedto compensate the color shift

FSTN: Foil compensated STN the foilcompensates the color shift

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u u

Different Cell Types II

900

TN

2700

STN

PolarizerGlassITO

Lightdirection

appearance:

gray / black yellow / greengray / blue

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Different Cell Types III

DSTN

2700

FSTN

PolarizerGlassITO

Lightdirection

appearance:

2700 2700

u u

compensationfoil

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Display types

Two different display modes are possible: positive and negative image.

Positive image is achieved when the 2 polarizer directions differ by 90

For negative image, the 2 polarizers must have the same orientation

positive mode

negative mode

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LCD LCDLCD

transmissive reflective transflective

mirror

Illumination Methods

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LCD Driver Theory

IntroductionTN cell Characteristics

Driving Scheme Characteristics

Driving Scheme meets TN cellOverview of Driving Schemes

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TN cell Characteristics

T/T0

1

0Vth V Vsat

Display off Display on

Brightness

VRMS(V)

Transmission - Voltage characteristic

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Important parameters

Threshold voltage Vth

RMS voltage for 10% relative transmission

Saturation Voltage Vsat


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Important parameters

TV curve of a normally black display

VRMS

T OFF

ON

100%

Relativetransmission

Vth

10%

Vsat

90%

Threshold voltage Vth


Saturation Voltage Vsat


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Important parameters Steepness S

measure for the slope of the curve between threshold and saturation

voltage

%100)1([%] th

sat

V

VS

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Important parameters Switching time Tsw

TswON defines the time it takes in order to reach from 10%

transmission to 90% transmission when increasing the RMS voltage

from Vth to Vsat

TswOFF defines the time it takes in order to reach from 90%

transmission to 10% transmission when decreasing the RMS voltage

from Vsat to Vth

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Important parameters Cell Power

fCVP cellcellcell 2

2

1)(thV

dA

cell withC

2)(2

2

th

dA

V

V

cell

V

fkfP

th

cell

krepresents the constants. Pcell proportional with 2thV

f

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Important parameters Cell Power

fCVP cellcellcell 2

2

1)(thV

dA

cell withC

2)(2

2

thd

A

V

V

cell V

f

kfP thcell

Pcell total cell power

Vcell voltage the cells driven by

Ccell total cell capacitance

f frequency of the driving signal

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Dependencies

TV curve (Vth)

frequency dependent

temperature dependent

Switching time

temperature dependent

Cell power

frequency dependent

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LCD Driver Theory

Introduction




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RMS voltage generation Matrix Addressing

Vrow

Vcol

dtVVT

V

T

rowcolRMS 0

2)(1

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Important Parameters

ON driving voltage VON

Max. RMS voltage that can be generated with a certain driving

scheme and a given bias system

OFF driving voltage VOFF

Min. RMS voltage that can be generated with a certain driving scheme

and a given bias system

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Important Parameters

bias voltage ratio a

Ratio between the row and column bias voltage levels

in Alt & Pleshko (one row at a time) driving

bias voltage range VLCD

Max. bias voltage minus min. bias voltage

)2( 22

aNap

NONLCD VaV

d

s

V

Va

OFFaNa

aNa

ON

VV

2

22

2

Important Parameters Formulas

Bias voltage ratio

ON driving voltage

Bias voltage range

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LCD Driver Theory

Introduction




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Driving Scheme meets TN cell

Important parameters Contrast Ratio

Steepness S (in case of optimum contrast)

OFF

ON

V

VCR contrastoptimumfor

th

sat

V

V

%100)1([%] OFF

ON

V

VS

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Driving Scheme meets TN cell

TN dependency compensation

Temperature dependent OFF driving voltage

Compensates for Vth drifts due to temperature variations

Temperature dependent frame frequency Compensates for switching time changes due to temperature

variations

Allows to reduce power consumption by having always the lowest

acceptable frame frequency

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LCD Driver Theory

Introduction




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Direct drive

Segments Common/

Back planeNumber of interconnections: N+1

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Direct drive

The wave forms BP and

Sn are generated in the

LCD driver. The electric

field state_n is

experienced by the

segment (pixel).

BP

state 1

Sn+1

Sn

state 2

Tframe LCDsegments

segment on

segment off

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Multiplexed drive

Com1 Com2

Segments

Back-planes

Number of interconnections: N/2 +2

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Multiplexed drive

BP0

BP1

state 1

Sn+1

Sn

state 2

TframeLCD

segments

segment on

segment off

The wave forms BPn

and Sn are generated in

the LCD driver. The

electric field state_n is

experienced by the

segment (pixel).

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Interconnects

The number of interconnections to theLCD cell can be calculated as:

S = total number of segment (pixels)

M = multiplex rateN= S/M + M e.g. 160 segments

1:4 multiplex

N = 44

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DC C ti


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DC Compensation

DC-compensation The liquid crystal properties deteriorate if a DC-field is applied:

100s mV: show off a burn-in effect (off pixels are visible)

1000s mV: start to decompose the liquid crystal

DC-compensation techniques:

Pulse inversion

Frame inversion

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DC C ti T h i


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DC-Compensation Techniques

Pulse inversion Frame inversion

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M lti l i V lt


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Multiplexing Voltages

To generate the different signals for row and column outputs,

staggered square waves are used. The number of levels can be

optimized for each multiplex rate. This intermediate voltages are

referred to as bias voltages. They can be evenly spaced, for minimal

operation voltage Vop.

Vop is the peak-to-peak voltage of the signals. Vth is the threshold

voltage, a physical parameter of the liquid crystal. Vop can now be

calculated for a needed mux-rate.

The viscosity of the liquid crystal increases with lower temperatures.

Therefore the Vop must be enlarged, to achieve identical twist of themolecules. A typical figure of the temperature coefficient is -15mV/ C.

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T i l Bi V lt G ti A hit t


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Typical Bias Voltage Generation Architecture

Vref

vdd phi0 phi0phi1 phi1

phi0 phi1QPrunCharge Pump

Control Logic

Vop

Vlcd_out

Vlcd_in

Charge Pump Vlcd Monitor

Bias Level

Generator

Rito

Rito

Cvlcd

Row

&Col

Muxes

Display

SequencerBiasCtrl

RowCtrl

ColData

BiasLevelsRamCtrl

LCD

Display

Rows

Cols

Vlcd

Vlcd_mon

Vlcd_sense

Rito

Display

RAM

I/O

interface

local

oscillator

frame

Vcol_on

Vcol_off

Vrow_unsel

Vrow_sel

vlcd

Vrow

N&P

N&P

sel

sel

Vcol

onN&P

onN&P

V6

V1

V2

V5

V1

V6

V3

V4

V1

V2

V3

V4

V5

V6

R

R

nR

R

R

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Chi O Gl ( COG )


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Chip On Glass ( COG )

Principle

Technology

Manufacturing

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P i i l f Chi O Gl


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Principle of Chip On Glass

Comparison: Conventional vs. Chip On Glass

only 1

IC

chip

12

3

4

5 LCD

PCB

COG

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Chip On Glass Technology


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Chip On Glass Technology

chip

gold-bumps17m height

conductiveglue

ITO

glass

LCD cellepoxyunderfill

The chip is attached to the extended glass ledge ofthe display module

silver dot

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Chip On Glass Manufacturing


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Chip is

delivered withGold bumps


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Flip the chip

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anisotropicconductive filmLCD cell

LCD driver


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pressure

UV light

F

F


F Pressure

UV light

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Chip On Glass Benefits


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Chip On Glass Benefits

Cost effective

No package

Dies with gold bumps

No package qualification

Very high yield:

~97%

High reliability No package mounting and soldering on PCB

High quality

Reduced resistance

Reduced coupling

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Evaluation Kits

&Support

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OM10088 Segment Driver Demo Board


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OM10088 Segment Driver Demo Board

PCF8562 Demo Board Low cost 2-chip solution for LCD User

Interface

Flexible layout supports 3 microcontroller

options

10 pin HVSON to 28 pin PLCC package

1KB to 8KB internal Flash memory

8-character alphanumeric LCD

I2C based LCD driver with 128 segment

support

Powered by a single 3V coin cell battery

Two miniature push-buttons for user control

Reprogrammable by user via 10-pin ICP

header

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OM6290 LCD Driver Demo Board


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OM6290 LCD Driver Demo Board

Block Diagram

PCF8531 PCF2119 PCF8576D

Text +Icons

module

Graphicmodule

PCA9633

LPC2148(ARM7)

I2C USB

LED backlight control

Source of display cells and display modulesavailable on dedicated OM6290 website.

Software stacks in C can be downloaded from thesame NXP web site:

http://www.standardics.nxp.com/support/boards/lcd.demo.board

Type OM6290

12NC 9352 861 74598

Order Can be ordered from NXP eSample store

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LCD Internet Pages and Application Notes


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LCD Internet Pages and Application Notes

LCD Internet Pages Main page

http://www.ics.nxp.com/products/lcd.drivers/

Application Notes AN10170

Design Guidelines for COG modules with NXP monochrome LCD drivers

http://www.ics.nxp.com/support/documents/interface/pdf/an10170.pdf

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Summary


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Summary

Three families of LCD drivers :

Segment, Character and Graphic or Dot-Matrix

Advantages of using a dedicated LCD driver

LCD Driver Theory

Chip-On-Glass (COG) Technology

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Lcd Driver Webinar Final File 2011

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