AR1020-I/ML Microchip Technology, AR1020-I/ML Datasheet - Page 29

• Manufacturer Part Number: AR1020-I/ML
• Description: IC TOUCH SCREEN CTRLR 20-QFN
• Manufacturer: Microchip Technology
• Type: Resistiver

Specifications of AR1020-I/ML

• Resolution (bits): 10 b
• Touch Panel Interface: 4-Wire, 5-Wire, 8-Wire
• Number Of Inputs/keys: 3 Key
• Data Interface: I²C, Serial, SPI™
• Voltage - Supply: 3.3 V ~ 5.5 V
• Current - Supply: 17mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 20-VQFN Exposed Pad, 20-HVQFN, 20-SQFN, 20-DHVQFN
• Voltage Supply Source: Single Supply
• Controller Type: Touch Screen
• Ic Interface Type: I2C, SPI
• Supply Voltage Range: 3.3V To 5V
• Operating Temperature Range: -40°C To +85°C
• Digital Ic Case Style: QFN
• No. Of Pins: 20
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sampling Rate (per Second): -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

8 BASICS OF RESISTIVE SENSORS
8.1 Terminology
ITO (Indium Tin Oxide) is the resistive coating that makes up the active area of the touch sensor. ITO is a
transparent semiconductor that is sputtered onto the touch sensor layers.
Flex or Film or Topsheet is the top sensor layer that a user touches. Flex refers to the fact that the top layer
physically flexes from the pressure of a touch.
Stable or Glass is the bottom sensor layer that interfaces against the display.
Spacer Adhesive is a frame of adhesive that connects the Flex and Stable layers together around the perimeter.
Spacer Dots maintain physical and electrical separation between the Flex and Stable layers. The dots are
typically printed onto the Stable layer.
Bus Bars or Silver Frit electrically connect to the ITO on the Flex and Stable layers to the sensor’s interface tail.
Bus bars are typically screen printed silver ink. They are usually much lower in resistivity than the ITO.
X-Axis is the left and right direction on the touch sensor.
Y-Axis is the top and bottom direction on the touch sensor.
Drive Lines supply a voltage gradient across the sensor.
8.2 General
Resistive 4, 5, and 8-wire touch sensors consist of two facing conductive layers, held in physical separation from
each other. The force of a touch causes the top layer to move and make electrical contact with the bottom layer.
Touch position measurements are typically made by applying a linear voltage gradient across a layer or axis of
the touch sensor. The touch position voltage for the axis can be measured using the opposing layer.
A comparison of typical sensor constructions is shown below.
© 2009 Microchip Technology, Inc.
4 Wire
5 Wire
8 Wire
Table 10 : Sensor Comparison
Sensor
Less expensive than 5-wire or 8-wire
Lower power than 5-wire
More linear (without correction) than 5-wire
Touch inaccuracies occur from flex layer damage or resistance changes
Maintains touch accuracy with flex layer damage
Inherent non-linearity often requires touch data correction
Touch inaccuracies occur from resistance changes
More expensive than 4 wire
Lower power than 5 wire
More linear (without correction) than 5-wire
Touch inaccuracies occur from flex layer damaged
Maintains touch accuracy with resistance changes
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