AT42QT1040-MMH Atmel, AT42QT1040-MMH Datasheet - Page 21

• 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

3.1
3.2
3.2.1
Touch Sensors Design Guide
Introduction
Planar Construction
Introduction
This section describes how you design zero-dimensional sensors using a self-capacitance
implementation (see
implement keys for use with QTouch sensor controllers.
The guidelines for constructing a self-capacitance sensor depend on whether the construction is planar
(that is, the electrodes that form the sensor and the traces are on the same insulating substrate) or non-
planar (that is, the electrodes are on the inner surface of the panel and separated from the main circuit
board). These two types of construction are discussed in the following sections.
With planar construction, both the electrodes and the traces for the sensor are fabricated on the same
plane of the insulating substrate (for example, a PCB or Flex PCB).
What is interesting about this type of construction is that the PCB can be one-sided, with both the
components and electrodes on the side away from the user’s finger. The electrode “back-fires” its
electric field through the PCB, the adhesive layer, and the panel. Atmel’s QT devices are unique in
having a sufficient signal range to detect through thick panel construction, and yet remain highly reliable
and sensitive (10 mm is a common stack thickness for QT sensor circuits). This results in a very low-cost
touch panel.
Figure 3-1.
“Back-firing” Sandwich-style Touch Panel
Self-capacitance Zero-dimensional Sensors
Section 1.2
Electrode Area
Electrode
and
Section
1.3). These styles of sensors are typically used to
Components
Field Flow
Panel
Adhesive
Substrate
Section 3
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3-1