QT60168C-ASG Atmel, QT60168C-ASG Datasheet - Page 9

• Manufacturer Part Number: QT60168C-ASG
• Description: IC TOUCH SENSOR 16KEY 32TQFP
• Manufacturer: Atmel
• Series: QMatrix™, QProx™r
• Type: Capacitiver

Specifications of QT60168C-ASG

• Number Of Inputs/keys: 16 Key
• Resolution (bits): 9, 11 b
• Data Interface: Serial, SPI™
• Voltage - Supply: 3 V ~ 5 V
• Current - Supply: 25mA
• Operating Temperature: -40°C ~ 105°C
• Mounting Type: Surface Mount
• Package / Case: 32-TQFP, 32-VQFP
• Output Type: *
• Interface: *
• Input Type: *
• For Use With: 427-1087 - BOARD EVAL QT60248-AS QMATRIX
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Touch Sensors Design Guide
Capacitance (C) is defined in
Equation 1-1. Capacitance
It should therefore be clear that thinner panels and higher dielectric constant materials yield higher
capacitance change during touch and hence a higher gain and a better SNR.
Materials” on page 2-5
Figure 1-2.
In the context of capacitive sensors, SNR is defined as in
of the touch signal levels.
Equation 1-2. SNR
1. Note that this definition uses the RMS noise present during touch, as this is the worst case.
T
Touchscreen Panel
Touch Area (A)
SNR(dB) = 20Log( TouchStrength / NoiseTouched
TouchStrength = SignalTouched
NoiseTouched
where:


C
AVG100 means the simple numeric average of 100 data points, typically taken evenly
spaced over a period of 2 seconds.
RMS100 means the root-mean-square of 100 data points, typically taken evenly
spaced over a period of 2 seconds, using the AVG100 figure as a baseline.
=

------------------------- -
0
discusses the thickness of the panel and its effect on the SNR.
Overlying Panel ( )

T

r

A
Equation
RMS100
=
e
1-1.
r
n
--------------------------------------------------------------------------------------------------------------------- -
n

=
=
99
0

Signal n   SignalTouched
AVG100
- SignalUntouched
–
Equation
100
RMS100
1-2.
Introduction To Sensor Design
(1)
)
AVG100
AVG100
See
Section 2.3.3 “Front Panel
Figure 1-3

2
Sensor
Behind
Panel
10620D–AT42–04/09
for definitions
1-3