AT42QT1040-MMH Atmel, AT42QT1040-MMH Datasheet - Page 33

• 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

4.1
4.2
4.2.1
Touch Sensors Design Guide
Introduction
Planar Construction
Introduction
This section describes how you design zero-dimensional sensors using a mutual-capacitance
implementation (see
implement keys for use with QMatrix sensor controllers.
As with a self-capacitance zero-dimensional type sensor, the guidelines for constructing a mutual-
capacitance sensor depend on whether the construction is planar or non-planar. The guidelines for 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).
Field propagation relies heavily on the overlying panel as most of the coupling field flow is horizontal
(see
adhesive, and that air bubbles are avoided during lamination; bubbles that are too large or too numerous
can give rise to significant unit-to-unit variation.
Figure 4-1.
The X and Y electrodes are designed to optimize the distribution of the electric field that is coupling
through the overlying panel. This maximizes touch sensitivity, as the touching object (typically a finger)
has the maximum opportunity to disrupt this field coupling and cause a touch to be detected.
Figure
4-1). It is important to make sure that the sensor is firmly laminated to the panel with
Mutual-capacitance Zero-dimensional Sensors
Field Flow
Front
Panel
PCB
Section 1.2
Electrode (X)
and
Drive
Section
1.3). These styles of sensors are typically used to
Electrode (Y)
Receive
Adhesive
Section 4
10620D–AT42–04/09
4-1