capacitive touch
TRANSCRIPT
Touch Technology
Touch Technology An Overview
Touch Technology
Table of Content Atmel’s Touch Technology
Division
Market presence
Technology Overview
Changing product design
Competing Technologies
Software Library
Touch screen solutions
Summary
Touch Technology
Atmel’s Touch Technology Division
Founded as Quantum Research
Group in 1996
Located in Southampton,
UK
Part of Atmel corp since March 2008
Solutions in production for
>12 years
Leaders in capacitive sensing
technology
Technology: charge-transfer
Substantial patent base
Flexible Business Models
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Market success to date
Mobile handsets Shipped in over 50M handsets
Over 200M buttons rotors and sliders in handsets
Over 5m touchscreens
Customers include Nokia, Motorola, Samsung, Bird, Sagem and Toshiba.
Note books Shipped over 2 million buttons and sliders
Buttons and sliders for function keys
On/Off buttons
Shipping in models for HP, Dell and Lenovo
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Market Success
Kitchen Appliances Shipping in appliances for over 8 years successfully
More that 20 design wins in various global manufacturers
Applications in cooker hobs, cooker hoods (extractors) microwave controls, refrigerator controls and dishwasher controls.
Customers include LG Appliances, GE, Whirlpool, Electrolux, Gorenje, Samsung, Haier
Consumer Electronics Multiple wins in desktop monitors
Multiple wins in MP3 apps
Customers include Apple, Philips, Samsung, LG, Bose, Logitech, Neovo, Asus, Acer
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Technology Overview
For 1 to 10 buttons Simple key shapes Easy to wire
QTouch™ QSlide™QWheel™
Linear touch Rotary touch 3 channels High resolution
QMatrix™
Up to 48 keys Water resistant High temperature
QField™
QTwo™
Single-touch screens
Multi-touch screens
Functionality also implemented through Atmel Touch Software Library™ – part of AVR® studio
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QTouch™
QTouch – simple solution 1-10 keys
1.8V operation Low power operations UART, SPI and I2C Always stays calibrated Patented Adjacent Key Suppression™(AKS™)
Supports small keypads
Small footprint – ideal for mobile devices Supports clear discrete button touch screens Most popular in the consumer market
QTouch – Popular in consumer market
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QTouch Basics: Goals
Detect finger presence near electrode
Electrode behind a dielectric panel so no direct galvanic connection to measuring circuit
Electrode
Measuring Circuit
Measuring Circuit
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9
QTouch Basics: Charge Transfer Basics
Cs >> Cx example (1000:1 ratio)
Cs = 10nF Cx = 10pF
S1,S2 and S3 are CMOS IO pins switching between GND, Z and Vdd
Cs
GND
GND
VDD
S1
S2
S3
Sampling capacitorMCU
CxEART
H
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QTouch™: Charge Transfer Basics
Uses a switched capacitor method employing a “sampling” capacitor Cs Usually 1000+ times bigger than the sense electrode capacitance Cx (normally around 1pF to 10pF)
The sense electrode is just an “open circuit” pad We measure the “self capacitance” of this pad
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QTouch™: Charge Transfer Basics
Cs is switched using “bit banging”
A series of voltage pulses cause current to flow in Cs and Cx Charge on Cs builds up by each pulse Cx is discharged after each pulse
The voltage over the Capacitor (U = Q/C) builds up as well
We measure the voltage by checking a digital input Like a comparator, comparing vs VIH
We measure the number of pulses to reach VIH
When we touch the sensor, the number of pulses will be decreased
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QTouch Basics: Charge Transfer Basics
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
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Step 1: Discharge Cx and Cs
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
Create Initial condition: Takes time
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Step 2: Float Cs
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
Prevents cross-conduction between P and N-channel transistors in *some* MCU IO cellsWell designed I/O blocks does this automatically
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Step 3: Charge Transfer
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
Rising edge on SNS pin drives charge through Cs into Cx
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Step 4: Float Cs and settling time
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
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Step 5: Measure Vcs and discharge Cx
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
SNS = Vcs
SNSK = Gnd
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Step 5: Measure Vcs and discharge Cx
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
SNS = Vcs = VDD * (Cx / (Cs + Cx))
Cs = ~ 1000 * Cx
Vcs = VDD / 1000
Qs = Cs * Vcs
Qx = Cx * Vx
Vx == 0 ==> Qx == 0 SNSK = Gnd
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Repeat 1 - 5:
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
Vcs = VDD / 1000 initially
Add approximately 0,999 * VDD * (Cx / (Cs + Cx))
Gnd
Qs = Cs * Vcs
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Continuously add charge to Cs
VIH
When Vcs reached VIH, the I/O port will read as ”1”.
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Real Waveform
Vcs
Time
Vdd
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Charging Waveform
Vsns
Time
Vih
Vdd
Vsnsk
Time
Vdd
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Normal mode
Typically uses ~200 pulses to reach VIH
Typical burst length = 500 us .. 5 ms Long burst lengths mainly for proximity detection
Run several bursts before declaring detection ”Detect integration - DI”
Similar to debouncing
DI count normally from 3 upwards, 10 = common
Hysteresis: detection level changes on detect
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Add a finger => Ct increase
Cs
Sampling capacitor
MCU
CxEART
H
GND
VDD
S2
S3
GND
S1
Vcs = VDD / 1000 initially
Add approximately
0,999 * VDD * (Cx//Ct / (Cs + Cx//Ct))
Gnd
Qs = Cs * Vcs
CtEARTH
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Effect of increasing Ct
The charge added each pulse will increase.
Cs will charge faster, than if no finger is present
VIH is reached faster
Fewer pulses are needed
Burst time gets shorter
Burst change (delta) is proportional to Ct
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Continuously add charge to Cs
VIH
When Vcs reached VIH, the I/O port will read as ”1”.
No fingerFinger present
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QTouch™: Sensitivity
Larger key surface area = more sensitivity
Sampling Capacitor, Cs controls sensitivity Increasing Cs = Increased differential sensitivity
makes the burst length longer
Improves resolution
Simple tuning procedure Changing a single capacitor value per key
Can be done without software
One time tuning for a design
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Technology Overview
For 1 to 10 buttons Simple key shapes Easy to wire
QTouch™ QSlide™QWheel™
Linear touch Rotary touch 3 channels High resolution
QMatrix™
Up to 48 keys Water resistant High temperature
QField™
QTwo™
Single-touch screens
Multi-touch screens
Functionality also implemented through Atmel Touch Software Library™ – part of AVR® studio
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QMatrix™
• UART, SPI and I2C• Efficient X-Y interleaved electrodes • Support up to 48keys • Low power operations• 1.8V operation• Always stays calibrated• Available in small packages (up to 24 Keys)• Patented Adjacent Key Suppression™(AKS™) for small keypads• Low power and small footprint – ideal for mobile devices• Supports clear discrete button touch screens• Most popular in the consumer market
QMatrix - Popular in appliance market and mobile market
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Self Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
…
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Mutual Capacitance
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Mutual Capacitance
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Mutual Capacitance
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QMatrix™: Charge Transfer Basics
Also uses a switched capacitor method employing a “sampling” capacitor Cs that is usually 1000+ times bigger than
the sensor capacitance Cx (normally around 1pF to 5pF)
The sensor in this case is formed at the “intersection” of two electrodes, X (transmitter) and Y (receiver).
In other words QMatrix measures the *mutual* transverse (usually) coupling capacitance between X and Y
X and Y Fixed number of voltage pulses Each pulse cause current to flow in Cx and Cs (in series with each other) Current only flows in selected pairs or Cx and Cs. This is how a sequential matrix scan is achieved
The voltage on Cs builds up pulse-by-pulse and after the fixed number of pulses is done, the voltage on Cs is measured to give us our reading
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QMatrix™: Charge Transfer Basics
Cs
GND
GND
VDD
S1
S2
S3 Sampling capacitor
MCU
CxGND
S4
X
Yk
Y
Vyk
|Vcs|
Time
Approximately linear
0.25V
Approximately linear
Vsns
Time
-0.25V
t
Terminal voltage
Y0
Y1
X0
X1
X2
X3
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QMatrix™ : Measuring Technique
We can use Atmel AVRs e.g. Tiny44/84/88, Mega48/88/168 (including PicoPower), Mega164P/324P for QMatrix because they have the
required internal comparator + counter/capture registers
Cs
GND
GND
VDD
S1
S2
S3
MCU
CxGND
S4
X
Yk
Y
Rsmp
SMP
CAPTURE
CTR CLK
+-
VDD
S5
GND
S6
Vcs
Time
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QMatrix™ Basics: What Happens During Touch ?:
Now we bring a finger close to electrode
This diverts charge from Cx, and so away from Cs
So each charge pulse now charges Cs by a smaller amount
This means charge builds up in Cs less quickly
So if each pulse deposits less charge, then Vcs rises slower, so
reaches a smaller terminal voltage
needs less time to discharge to GND
so counter value gets less
count change (delta) is proportional to Ct
E-field
X Y EARTH
Ct
Vcs
Time
No touch
Delta
Time
Touch
Vcs
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QMatrix™: Sensitivity
Optimise key designs for improved sensitivity and SNR
Increasing Burst Length (number of charge pulses), increases sensitivity Software based tuning Does not require component changes
Increasing Rsmp, increases signal resolution
One time tuning for a design
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Best in class solutions: Excellent signal-to-noise ratio Excellent field penetration Spread spectrum modulation Failure mode detection Best in class EMC characteristic
Ease of design: Highly integrated solutions Reference designs
Flexible: Standard or custom products User developed solutions
Cost effective
Atmel’s Charge Transfer Technology
QMatrix™ charge transfer principle
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Technology Overview
For 1 to 10 buttons Simple key shapes Easy to wire
QTouch™ QSlide™QWheel™
Linear touch Rotary touch 3 channels High resolution
QMatrix™
Up to 48 keys Water resistant High temperature
QField™
QTwo™
Single-touch screens
Multi-touch screens
Functionality also implemented through Atmel Touch Software Library™ – part of AVR® studio
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Usable over LCD display iPod-type functionality Low voltage, low power Slider/Wheel available in
QTouch devices: QT1106 Slider available in QMatrix
device: AT42QT2160 Only three channels used to
make a 256 position absolute scroller
QSlide™ & QWheel™ - Easy scrolling
QSlide/QMatrix - Popular in personal media devices
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QSlide™ & QWheel™: QTouch™
i) Small 10-12mm dia
ii) Medium 12-16mm dia iii) Large 16-40mm dia
i) Small 20-25mm long
ii) Medium/Large 25-60mm long
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QSlide™ & QWheel™: QMatrix™
X0 X1 X2 X3
Y
Y
X0
X1
X2
X3X4
X5
X6
X7One Layer Designs
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QSlide™ & QWheel™: QMatrix™
2 Layer Designs - Flooded X
Increases design possibilities
Improved directional noise immunity
Y
X0
X1
X2X3
X4
X5
Y
X0 X1 X2 X3
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QSlide™ & QWheel™ : Touch Position
A BSS
XX
L E F T RI G H TRI G H T
A
BC
Uses geometric calculations in between 2 points (channels) to determine absolute touch position
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Capacitive sensing - changing product design
Flexible No longer restricted to
using buttons
Increasing focus on industrial design
UI innovation with multi-touch
Innovative Slimmer products - no
mechanical parts required
Easy to clean
Hidden until lit
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Other Markets
Capsensing is not only for Mobile and appliances….Atmel have many design wins in …..
Medical
Automotive
Industrial
Vending
Security
Toys
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Atmel Industry Presence : recent design wins
ConsumerMobile and PND
Mobile phonesSmart phones
HeadsetsPNDs
LaptopsDigital photo frames
TVs and Home cinemasStereos and speakers
MP3 players
Appliance
OvensRefrigerators
Washing machines
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Atmel advantages
Early market entry – long experience
Addresses many diverse markets
Robust solution Very few competitors are even close
Competitor analysis data available on request
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Differentiation: Atmel Touch Sensors Very high signal to noise ratio
Makes designs easier from the outset
Supports small sensors
OK in noisy environments
Broad range of key sizes & shapes due to size of integration capacitors
Inherent flexibility of technology
Key patent for close pitched key arrays Adjacent Key Suppression (AKS™)
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QMatrix Strong suppression of moisture effects
Due to X and Y electrode design and touch aquisition
Remote placement of chip Sensitive to X/Y crossing
Not sensitive to X lines
Not sensitive to Y lines
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QTouch/QMatrix on AVR AVR has plenty of processing power.
Can complete sensing faster
Can spend more time in sleep
Minimal amount of H/W needed Chip resource available for other applications
Lower power consumption
Broad range of applications with a lower cost chip
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Q-Touch/Q-Matrix libraries
Empowering Atmel AVR users with
Touch Sensor Technology
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Aims of libraries
Flexible, high performance capacitive sensing firmware
Well proven capacitive sensing solution
Support for buttons, sliders and wheels
Easy to implement
No license fee
Can coexist with user application
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Advantages of the Atmel Code Module
Recognised industry leading Charge Transfer technique Best signal to noise ration
Makes designs fundamentally easier to implement
Flexible implementation arbitrary key sizes & shapes no need to balance channels
All digital technique None of the disadvantages of analogue sensing techniques
Easy implementation using Quantum reference designs
Access to key Atmel/Quantum patents Adjacent Key Suppression
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Advantages of the Atmel Code Module
Uses AVR as the hardware platform AVR32, Cortex-M3 to follow
Industry leading microcontroller price / performance
Lowest power consumption
Broad product range can be developed & implemented
Fully flexible user implementation
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Advantages of the Atmel Code Module
Simple, easy to implement code library Robust front end capacitive acquisition
Highly experienced Quantum Atmel team Applications / implementation support
Low cost solution
No license cost
Support provided by the Atmel FAE’s
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Code Module Availability
Code modules will be available in two basic versions QTouch module – recommended as first approach
- High sensitivity
- High system noise tolerant
- Easy design
QMatrix module- Less pins needed for 3+ channels
- More tolerant of moisture and ground loading
- Electrode design needs care
Support packages available in both cases Library module and API GUI front end Evaluation module & PC Application Software Reference implementation & application note
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Atmel Touch Software Library - Flexible
Available on standard Atmel parts using libraries in AVR studio
Environmental changes tracked and compensated
Error conditions detected and corrected
Works seamlessly with main device application
For volume programs, application and code development available
Atmel TouchSoftwareLibrary
Host App
Host App
Atmel TouchSoftwareLibrary
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Atmel Capacitive Touchscreen Solutions
Two Touch™ and Single Touch Touchscreens
Roadmap for Touchcreens
January 2009
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Projected Capacitive Touch Screens
Sensors realised with patterned conductors Usually realised using ITO/PET or ITO/Glass
Mostly 2+ layers, Atmel’s solution supports single layer sensors
Multiple sensing elements
Sequential sensing
Atmel’s QField™ technology
Advantages Excellent signal to noise ratio
Accuracy across the whole surface
Can support multiple touches
Senses through ‘thick’ dielectric materials
No user calibration needed
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Introducing the QT5000 Family
Two Touch™ for the most intuitive user interfaces
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QT5000 Family Unique Value
The QT5320 and the QT5480 are single chip Two Touch™ touchscreen controllers supporting
single and two finger touch
Currently up to 48 channels (8X x 6Y)
Supports Single Touch and Dual Touch
Many common touch gestures integrated
Standard touchscreen reference designs available
Highly user configurable interface
Small 5mm x 5mm BGA package
Low power, low voltage
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Introducing the QT4000 Family
Touchscreen solution with single layer sensors for the thinnest possible implementation
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QT4000 Family Unique Value
The QT4120 and the QT4160 are single chip touchscreen controllers enabling single layer
sensor designs
Currently up to 16 channels (4X x 4Y)
Supports Single Touch with Single layer sensors
Many common gestures integrated
Reference designs standard screen sizes
Small 5mm x 5mm QFN package
Low power, low voltage
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Components and Supply Chain
Atmel provides Touch controller IC
Controller board reference design
Sensor reference design
Integration support
Sensor test equipment design
Atmel Partners provide Tested and qualified sensor film
Integration of sensor and front panel
Production controller board
Note: Solution with integrated sensor, front panel and LCD can delivered
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Target Applications
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User Interface in Mobile Phones
Touchscreen mode Managing the address book
Managing the photo album
Fixed keys and sliders On/Off keys
Special function keys
Volume controls
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User Interface in Media Players
Touchscreen mode Music control
Photo control
Zoom and Rotate
Fixed keys and sliders On/Off keys
Special function keys
Volume controls
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User Interface in Navigation Systems
Touchscreen mode Controlling the maps
Zooming in and out
Fixed keys and sliders On/Off keys
Special function keys
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Other Target Applications
Digital still cameras
Digital picture frames
Appliance control
Gaming devices
PDAs
Displays
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Easy System Designs
Touchscreens, sliders, wheels and/or keys, selectable by the host via the I2C compatible interface
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Appendix
Atmel’s Portfolio of Touch Sense Products
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QTouch™ - Key std. Products
Part Channels Package Temp. (OC) Eval.Board
QT100A 1 WSON-6 -40 to +85 E100S
QT220 2 SSOP-20 -40 to +85 E240B
QT240 4 SSOP-20 -40 to +85 E240B
QT1080 8 QFN-32 -40 to+85 E1080
QT1101 10 QFN-32 -40 to +85
QT1081 8 QFN-32 -40 to +85 E1081
QT1103 10 QFN-32 -40 to +85 E1103
QT1106 7 + Slider or Wheel
QFN-32 -40 to +85 E1106
AT42QT1040
4 QFN-28 -40 to +85 AT42EVK1040
AT42QT1060
6 QFN-28 -40 to +85 AT42EVK1060
Devices for 1 to 10 keys and/or sliders/wheels
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QMatrix™ - Key std. Products
Part Channels Package Temp. (OC) Eval Board
QT60160 16 QFN-32 -40 to +85 E6240
QT60168 16 TQFP-32 -40 to +105 E6248
QT60240 24 QFN-32 -40 to +85 E6240
QT60248 24 TQFP-32 -40 to +105 E6248
QT60326 32 TQFP-44 -40 to +105 E6486
QT60486 48 TQFP-44 -40 to +105 E6486
AT42QT2160 16
1 Slider
QFN-28 -40 to +85 AT42EVK2160
Controlling up to 48 keys and/or sliders/wheels
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Atmel Touch Library
AT42EVK2080A – QTouch module with ATmega88 target device Hardware module – user can view and evaluate trial implementations of
firmware 10 x ATMega88 IC’s
AT42EVK2080B – QMatrix module with ATtiny88 target device Hardware module – user can view and evaluate trial implementations of
firmware 10 x ATMega88 IC’s
Common to both evaluation modules Installation CD for PC configurator software Quickstart guide including basic operating / flashing instructions / what
hardware required Debug interface allowing rapid visualisation of the pre-processed capacitive
signals for diagnostics API document Description of interface & how to use Reference implementation Compile instructions Links to useful sources of additional code PC debug application for tuning implemented systems
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QField and QTwo Touchscreen Products
Easy to Use Touchscreen Controllers Part Total
nodesPackage Touch Screen
SizeEval Board
AT42QT4120 12 (4x3) QFN-32 Single touch 3.2” EVK4120A/B
AT42QT4160 16 (4x4) QFN-32 Single touch 4.3” EVK4160A/B
AT42QT5320 32 (8x4) QFN-32 Single touch
/Two touch
4.3” EVK5480x
AT42QT5480 48 (8x6) BGA-49 QFN-
44 TQFP-44 Single touch
/Two touch
8” EVK5480x