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
PCF85134 4 x 60 segments
PCF85133 4 x 80 segments
PCF85132 4 x 160 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 Character Drivers
LCD Graphic Drivers
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LCD character driver
I2C Bus /4/8bit parallel
characterRAM
controllogic
characterROM
displayRAM
sequencer
bias voltage generator
rowdriver
columndriver
Features
On-chip character generator
On-chip temperature compensation
On-chip character ROM and RAM
Low power consumption
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 Character 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
Low power consumption
Temperature compensation
LCD graphic driver
Serial /parallel /
I2C Interface
controllogic
displayRAM
sequencer
bias voltage generator
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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TN cell Characteristics
Important parameters
Threshold voltage Vth
RMS voltage for 10% relative transmission
Saturation Voltage Vsat
RMS voltage for 90% relative transmission
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TN cell Characteristics
Important parameters
TV curve of a normally black display
VRMS
T OFF
ON
100%
Relativetransmission
Vth
10%
Vsat
90%
Threshold voltage Vth
RMS voltage for 10% relative transmission
Saturation Voltage Vsat
RMS voltage for 90% relative transmission
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TN cell Characteristics
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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TN cell Characteristics
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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TN cell Characteristics
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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TN cell Characteristics
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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TN cell Characteristics
Dependencies
TV curve (Vth)
frequency dependent
temperature dependent
Switching time
temperature dependent
Cell power
frequency dependent
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LCD Driver Theory
Introduction
TN cell Characteristics
Driving Scheme Characteristics
Driving Scheme meets TN cellOverview of Driving Schemes
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Driving Scheme Characteristics
RMS voltage generation Matrix Addressing
Vrow
Vcol
dtVVT
V
T
rowcolRMS 0
2)(1
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Driving Scheme Characteristics
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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Driving Scheme Characteristics
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
TN cell Characteristics
Driving Scheme Characteristics
Driving Scheme meets TN cellOverview of Driving Schemes
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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
TN cell Characteristics
Driving Scheme Characteristics
Driving Scheme meets TN cellOverview of Driving Schemes
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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
Chip On Glass Manufacturing
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Chip On Glass Manufacturing
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Chip On Glass Manufacturing
Flip the chip
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Chip On Glass Manufacturing
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anisotropicconductive filmLCD cell
LCD driver
Chip On Glass Manufacturing
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Chip On Glass Manufacturing
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pressure
UV light
F
F
Chip On Glass Manufacturing
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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