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How to Address
Touchscreen Performance
Copyright © 2012 Synaptics Incorporated. All Rights Reserved. This information and any related goods and services are provided “as is.” Synaptics makes no
representations or warranties, expressed or implied. Synaptics providing you information, goods or services does not, by itself, create any express or implied license
under any patent, trade mark, trade secret, copyright, mask work right, or any other intellectual property right.
… back in the day
X Channels
Y Channels
?
?
 Profile ‘projects’ finger signals to X and Y axes
 The touchpad/touchscreen was one end of a parallel plate capacitor
 The finger was the other end
BUT
 Subject to fake fingers showing up
 Poor multi-finger disambiguation
 Non-linear, lots of jitter
 Not enough data for advanced user interaction (Pen? Proximity? Glove?)
Copyright © 2012 Synaptics Incorporated. All Rights Reserved
Page 2
Trans-Capacitive Image Sensing
How it works:
 Grid of electrodes: transmitters in one dimension, receivers in the other
 Capacitors at overlaps (pixels)
 Drive waveforms on transmitters, observe signal coupled to receivers
 Detect variance in capacitance at receiver when conductor (finger) is
introduced
Transmitters
Receivers
Copyright © 2012 Synaptics Incorporated. All Rights Reserved
Page 3
Trans-capacitive Image Sensing
How does the disruption occur?
 When a finger approaches, some of the field lines from the
transmitter will terminate at the finger
 Fewer field lines at Rx  reduction in capacitance
 Synaptics products work by measuring the reduction in
capacitance
Copyright © 2012 Synaptics Incorporated. All Rights Reserved
Page 4
Trans-capacitive Image Sensing
 Imaging captures richer image of finger signals
– Improved multi-finger disambiguation, can track more fingers
– Alleviates fake finger problems
Drive Rows
– More data enables better performance and functionality
Sense Columns
Copyright © 2012 Synaptics Incorporated. All Rights Reserved
Page 5
How do System-Level Parameters Affect Touch
Performance?
Lens
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Sensor
Flex
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What is the material and dielectric constant?
What is the thickness?
What is the optical quality (e.g. clarity, haze, reflectance)?
What is the trace resistance and cross-coupling?
How close do traces run to noise sources?
How long are the traces?
Display



 What is the material and dielectric constant?
 What is the thickness?
 What is the sensor pattern?
 Is there a shield?
 How large is the gap between the sensor and the
display?
What type of display is it?
How noisy is it?
What is the noise signature?
Power
 What is the power budget?
 How aggressive are the touch
controller sleep modes?
Touch Controller
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Host Software and UI
What are the chip resources?
How is the analog front end designed?
How effective are the fw algorithms?
What is the environmental noise?
Copyright © 2011
2012 Synaptics Incorporated. All Rights Reserved

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What is the GUI?
Is it designed for touch interactions?
What level of touch performance is needed?
What gestures are supported?
How responsive is the software UI?
Page 6
Designing for Touch: More than just a chip
δL
Cover Lens Glass
OCA
δOCA
PRx
δB
WTX2
GY
Rx/Tx ITO
Substrate Glass
GH
Glass
Shield ITO
PTx
γ
Discrete Sensor Stackup (1S1P)
δL
Rx/Tx
ITO
VCOM
ITO
Cover Lens Glass
OCA
Polarizing Film
δP
δCF
δOCA
WRX1
Rx(n-1)
Color Filter Glass
Finger deforming the sensor
Gxx
Gx
WRX2
PRX
GX
Rx
(n)
WE
Sensor-on-lens (G2)
Tx(m)
δL
Cover Lens Glass
OCA
Lens
WTX2
GTX
δOCA
δB
PTX
Wy
Gy
Tx(m-1)
WE
Rx/Tx ITO
Substrate Glass
PRX/4
Shield ITO
PRX/2
Air Gap
WRX
Discrete Sensor Stackup (1S2P)
PET
δL
Cover Lens Glass
Rx ITO
PET Core
Tx ITO
Airgap
PRx
Display
δOCA
δc
OCA
δP
Flexing sensor
δA
PTx
δCF
GTx
Polarizing Film
VCOM
ITO
Color Filter Glass
Receiver
Width
2-layer PET Sensor Stackup (2S2P)
 Synaptics’ years of experience in module design as well as a total systems
approach has culminated in an unparalleled understanding of sensor design and
stackups
 Sensor Designs are innovated and updated to address total system needs
 Software tools to enable customers, partners, and the ecosystem, in conjunction
with advanced firmware algorithms work with sensor designs for best in class
performance
 Various approaches for different end goals allowing customers to differentiate
their products
 Backed by over 1 billion units shipped
Copyright © 2012 Synaptics Incorporated. All Rights Reserved
Page 7
Beginning to End Tools for ClearPad design
The Synaptics Tool Suite is a beginning to end set of software that compliments
the entire Synaptics portfolio and simplifies design for:
 Faster Time-to-Market
 Greater flexibility
 Reduced Total Cost of Ownership
Synaptics SafeSense – ClearPad Sensor Simulation Tool
Sensor Pattern Generation and Simulation
Synaptics Design Studio – ClearPad Development Tool
ClearPad bring up, tuning, configuration,
exploration, and production test
Synaptics TestStudio – ClearPad Production Test Tool
Stand alone production test
Copyright © 2012 Synaptics Incorporated. All Rights Reserved
Page 8
THANK YOU!
Copyright © 2012 Synaptics Incorporated. All Rights Reserved. This information and any related goods and services are provided “as is.” Synaptics makes no
representations or warranties, expressed or implied. Synaptics providing you information, goods or services does not, by itself, create any express or implied license
under any patent, trade mark, trade secret, copyright, mask work right, or any other intellectual property right.