AT42QT1040-MMH Atmel, AT42QT1040-MMH Datasheet - Page 49

• 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

5.3
5.3.1
5.3.2
Touch Sensors Design Guide
Typical Spatially Interpolated Method
Introduction
Small Slider Or Wheel
A spatially interpolated wheel or slider sensor uses three electrodes, all directly connected to the sensor
chip. The form of the electrodes depends on the overall size of the slider or wheel.
Note that the designs shown in this section use the method of “two plus two half” electrodes so that they
are compatible with the spatially interpolated slider technique described in
Resistively Interpolated Method” on page 5-6
same sensor chip can drive either electrode style.
Note also that here and elsewhere in this guide, the order of the channels is determined by the chip used
and, in the case of a wheel, by the rotation of the wheel.
In the context of this document, a small slider is between 21 and 26 mm long and a small wheel is
between 12 and 20 mm diameter.
Note that because the slider or wheel is small in comparison with a typical finger, the linearity and usable
range on the sensor are compromised in favor of simple electrode geometries. A small slider uses
simple rectangular electrodes (see
(see
This design relies on both the touching finger and the front panel to interpolate the channels. Expect
these smaller electrodes to have low sensitivity and plan for front panels of 1.5 mm acrylic or less.
Figure 5-2.
Figure 5-3 on page
Small Slider (Spatially Interpolated)
Channel 0
5-4).
0.1–0.5 mm
Figure
Channel 2
5-2) and a small wheel uses simple wedge-shaped electrodes
from an algorithmic point of view. This means that the
Channel 1
6 8 mm
−
Self-capacitance One-dimensional Sensors
Half width
at end
5 15 mm
−
Section 5.4 “Typical
10620D–AT42–04/09
5-3