AT42QT1040-MMH Atmel, AT42QT1040-MMH Datasheet - Page 36

• Manufacturer Part Number: AT42QT1040-MMH
• Description: IC TOUCH SENSOR 4KEY 20-VQFN
• Manufacturer: Atmel
• Series: QTouch™r
• Type: Resistiver

Specifications of AT42QT1040-MMH

• Touch Panel Interface: 4, 2-Wire
• Number Of Inputs/keys: 4 Key
• Data Interface: I²C, Serial
• Data Rate/sampling Rate (sps, Bps): 200k
• Voltage Reference: Internal
• Voltage - Supply: 1.8 V ~ 5.5 V
• Current - Supply: 10mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-VQFN Exposed Pad, 20-HVQFN, 20-SQFN, 20-DHVQFN
• Output Type: Logic
• Input Type: Logic
• Supply Voltage: 1.8 V to 5.5 V
• Dimensions: 3 mm L x 3 mm W x 0.8 mm H
• Output Voltage: 0.7 V to 0.8 V
• Temperature Range: - 40 C to + 85 C
• Termination Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: AT42QT1040-MMH; AT42QT1040-MMHTR

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