QT60248C-ASG Atmel, QT60248C-ASG Datasheet - Page 36

• Manufacturer Part Number: QT60248C-ASG
• Description: IC TOUCH SENSOR 24KEY 32TQFP
• Manufacturer: Atmel
• Series: QMatrix™, QProx™r
• Type: Capacitiver

Specifications of QT60248C-ASG

• Number Of Inputs/keys: 24 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

10620D–AT42–04/09
Mutual-capacitance Zero-dimensional Sensors
4.2.2.8
4-4
Designs Resulting In Low Interdigitation
Figure 4-3.
As has already been stated, designs that result in a very small number of fingers should be avoided, as
such designs result in a poor SNR.
For example, if the following measurements are used in
then the calculation is as follows:
This results in the pattern shown in
T = 1.5 mm
W = 8 mm
H = 8 mm
Y
Results of Example Calculation
width
X
X
fingers
border
0.6 mm
= 0.1 mm
0.25 mm
=
=
=
= 1
= (8 - 1.5 - 0.1 - 1 x (2.25 + 0.1)) / 2
= (6.4 - 2.35) / 2
= 2.02 mm



(8 - 4.5 - 0.1) / (2.25 + 0.1)
3.4 / 2.35
1.45
Figure
10 mm


4-4.


0.5 mm
Equation
0.875 mm


4-6:
8 mm
Touch Sensors Design Guide