ATQT600 Atmel, ATQT600 Datasheet - Page 9

• Manufacturer Part Number: ATQT600
• Description: KIT EVAL TOUCH FOR QT600
• Manufacturer: Atmel
• Series: QTouch™r

Specifications of ATQT600

• Sensor Type: Touch Screen
• Interface: USB
• Embedded: Yes, Other
• Utilized Ic / Part: ATtiny88, ATmega324PA, ATxmega128A1
• Processor To Be Evaluated: ATtiny88, ATmega324, ATxmega128
• Data Bus Width: 8 bit, 16 bit
• Interface Type: USB
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Operating Supply Voltage: 1.6 V to 3.6 V
• Silicon Manufacturer: Atmel
• Kit Application Type: Sensor
• Application Sub Type: Touch Sensor
• Kit Contents: USB Bridge, MCU Cards, Touchpad Cards
• Svhc: No SVHC (15-Dec-2010)
• Mcu Supported Families: ATtiny88,
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Supply: -
• Sensitivity: -
• Sensing Range: -
• 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