AT42QT1070-MMH Atmel, AT42QT1070-MMH Datasheet - Page 8

• Manufacturer Part Number: AT42QT1070-MMH
• Description: IC TOUCH SENSOR 7KEY 20-VQFN
• Manufacturer: Atmel
• Type: Capacitiver

Specifications of AT42QT1070-MMH

• Number Of Inputs/keys: 7 Key (Comms), 5 Key (Standalone)
• Data Interface: I²C
• Voltage Reference: Internal
• Voltage - Supply: 1.8 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-VFQFN Exposed Pad
• Supply Voltage: 1.8 V to 5.5 V
• Dimensions: 3 mm L x 3 mm W x 0.8 mm H
• Temperature Range: - 40 C to + 85 C
• Termination Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Resolution (bits): -
• Touch Panel Interface: -
• Data Rate/sampling Rate (sps, Bps): -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

10620D–AT42–04/09
Introduction To Sensor Design
1.3
1.4
1-2
Dimension Groups
Some Important Theory
In addition to the self- and mutual-capacitance types described in
into three groups, depending on the number of dimensions they use (see



When considering the design of a sensor, you will need to consider both the sensor type and the
dimension group, making six possible combinations in total. The combinations for zero-dimensional and
one-dimensional sensors are discussed individually in
are not covered by this guide. For information on designing two-dimensional sensors, please contact
Atmel’s Touch Technology Division.
Figure 1-1.
You will need to be aware of the following terms when reading this document:







Zero Dimensional Sensors
Single point of contact
Key
Zero-dimensional sensors
A zero-dimensional sensor is one that represents a single point of contact. The typical implementation
of a zero-dimensional sensor is a key.
One-dimensional sensors
A one-dimensional sensor is one that detects the linear movement of a finger during touch (that is,
along a single axis). Typical implementations of one-dimensional sensors are sliders and wheels.
Two-dimensional sensors 
A two-dimensional sensor is one that detects the movement of a finger during touch along two axes.
Typical implementations of two-dimensional sensors are touchscreens and touchpads.
Cx: The electrode’s natural capacitance, separate from any parasitic capacitance


T: The thickness of the overlying panel in meters (see
A: The area of the touched region in square meters (see
Cp: Any parasitic capacitance added in parallel with Cx
SNR: Signal to noise ratio: a measure of the quality of the capacitive measurement
r
0
: The relative dielectric constant of the overlying panel material (see
: The capacitance per meter of free space, defined as 8.85 x 10
Sensor Dimensions
One Dimensional Sensors
Movement in one direction
Slider
Wheel
Section 3
Figure
Figure
1-2)
Two Dimensional Sensors
Movement in two directions
to
Touchscreen/
Touchpad
Section
1-2)
Section
-12
F/m
Figure 1-2 on page
Figure
1.2, sensors can also be split
Touch Sensors Design Guide
6; two-dimensional sensors
1-1):
1-3)