AT42QT1040-MMH Atmel, AT42QT1040-MMH Datasheet - Page 68

• 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
Glossary of Terms
A-2
Linearity
Multi-touch
Mutual-capacitance Sensor
Node
Non-planar Construction
One-dimensional Sensor
Panel
The measurement of the peak-to-peak deviation of the reported touch coordinate in one axis relative
to the absolute position of touch on that axis. This is often referred to as the nonlinearity.
Nonlinearities in either X or Y axes manifest themselves as regions where the perceived touch
motion along that axis (alone) is not reflected correctly in the reported coordinate giving the sense of
moving too fast or too slow. Linearity is measured as a percentage of the axis in question.
For each axis, a plot of the true coordinate versus the reported coordinate should be a perfect straight
line at 45°. A non linearity makes this plot deviate from this ideal line. It is possible to correct modest
nonlinearities using on-chip linearization tables, but this correction trades linearity for resolution in
regions where stronger corrections are needed (because there is a stretching or compressing effect
to correct the nonlinearity, so altering the resolution in these regions). Linearity is typically measured
using data that has been sufficiently filtered to remove the effects of jitter. For example, a 100 mm
slider with a nonlinearity of ±1 percent reports a position that is, at most, 1 mm away in either
direction from the true position.
The ability of a touchscreen to report multiple concurrent touches.
See also Two Touch.
A sensor with two connections to two parts of the sensor: an X (transmit) electrode, and a Y (receive)
electrode. The mutual capacitance from X to Y is measured by the sensor controller. This type of
sensor is suitable for implementating sensors for use with QMatrix
See also self-capacitance sensor.
One of the capacitive measurement point at which the sensor controller can detect capacitive
change. A node and a channel are really the same thing, but the term node is used in the context of a
touchscreen or slider as it conveys the sense of spatial distribution better.
See also channel.
A method of construction in which the electrodes are fabricated on the inner surface of the touch
panel, with the rest of the touch sensing circuitry on the main capacitive touch circuit board and
remote from the electrodes. This form of construction has several advantages over a planar form of
construction. See
See also planar construction.
A sensor 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.
The front, or uppermost, layer of a touchscreen or touchpad that is touched by the user. Common
front panel materials include glass, plexiglas, polycarbonate and PMMA.
Section 3.3 on page
3-7.
™
sensor
Touch Sensors Design Guide
controllers.