AT42QT1040-MMH Atmel, AT42QT1040-MMH Datasheet - Page 50

• 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
Self-capacitance One-dimensional Sensors
5.3.3
5-4
Medium/Large Slider Or Wheel
Figure 5-3.
In the context of this document, a medium/large slider is between 26 and 60 mm long and a
medium/large wheel is between 20 and 60 mm diameter.
A medium/large slider or wheel uses toothed electrodes (see
page
along the longitudinal axis of a slider or the radial axis of a wheel). Some transverse variation of the
reported position is inevitable
Note that there are some alternative methods of construction that are very similar to the method shown
here, but with some subtle changes in segment lengths and tooth gapping. These methods are normally
an attempt to optimize the intrinsic linearity of the slider or wheel. However, it is often more practical to
perform this linearization in software rather than trying many iterations of the electrode pattern during
development
1. That is, for a wheel, a movement “in to out” or “out to in” results in a small change in the reported angle. For a
2. A software linearization using a look up table, or perhaps piecewise-linear-interpolation is fundamentally not as
slider, this change happens when moving at 90° to the normal slide direction.
good as correcting the underlying electrode pattern because the non-linearity is locally corrected at the expense
of the resolution achievable.
5-5) to interpolate the capacitive change spatially as a finger moves across the sensor (that is,
(2)
Small Wheel (Spatially Interpolated)
.
(1)
Channel 2
, but is reduced by making the segments narrow (towards the 3 mm size).
5 mm
Channel 0
Channel 1
12–20 mm
Figure 5-4 on page 5-5
90°
Touch Sensors Design Guide
and
Figure 5-5 on