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1 Overview

1.3 User Interface Layout Options

The QT1106 can sense through all common plastics or glass or other dielectric materials up to 10mm thick. It can be used to implement a linear slider or rotary scroll wheel plus seven additional discrete keys. The slider or wheel indicatesabsolute positions.

1.1 Introduction

The QT1106 is an easy to use sensor IC based onQuantum’s patented charge-transfer (‘QT’) principles for robust operation and ease of design. This device has many advanced features which provide for reliable, trouble-free operation over the life of the product. In particular the QT1106 features advanced self-calibration, drift compensation, and fast thermal tracking. Unlike prior devices, the QT1106 can tolerate power supply fluctuations better in order to eliminate the need for a voltage regulator in many cases.

1.4 Slider and Wheel Construction

The QT1106 can connect to either a wheel or a linear slider element (Figure 1.1). Selection of wheel or linear operation is set through an SPI command. The basis of these designs isfound in US Patent 4,264,903 (expired). The first and last positions of the linear slider have largertouch areas.As with touch button electrodes, wheels and sliders can beconstructed as etched areas on a PCB or flex circuit, or from clear conductors such as Indium Tin Oxide (ITO) or screen- printed to allow backlighting effects, or for use over an LCDdisplay.

1.2 Burst Operation

The device operates in burst mode. Each key is acquired using a burst of charge-transfer sensing pulses whose count varies depending on the value of the sense capacitor Cs and the load capacitance Cx (finger touch capacitance and circuit stray capacitance).The channels’ signals are acquired using three successivebursts of pulses: Burst 1: B1, B3, B5, B7 (for discrete keys 1, 3, 5, 7)Burst 2: B2, B4, B6 (for discrete keys 2, 4, 6) Burst 3: A1, A2, A3 (for wheel or slider)Bursts always operate in 1, 2, 3 sequence as a group andoccur one right after the other with minimum delay. The groups are separated by an interval of time that can be usedfor SPI communications. Spread-spectrum operation - Bursts can operate over aspread of frequencies, so that external fields will haveminimal effect on key operation and emissions are veryweak.Spread-spectrum operation works together with the ‘detectintegrator’ (DI) mechanism to dramatically reduce the probability of false detection due to noise. An external RCcircuit is required to implement spread spectrum, but thiscircuit is optional.

1.5 QMagic

TM

Proximity Effect

Channel 7 of the QT1106 can optionally operate a ‘magic on’function based on hand or body proximity to a product. Byusing a relatively large electrode inside the product’s enclosure and a larger value of Csb7 (see Figure 2.1), theproduct can auto power up or activate its display with handapproach. This simple feature can add enormous sales appeal to almost any product.

1.6 SPI Interface

The QT1106 uses a five-wire SPI interface. In addition to thestandard four SPI signals (/SS, SCLK, MOSI and MISO),there is a DRDY (data ready) output for flow control.The QT1106 also provides a CHANGE signal to indicatewhen there has been a change in detection state. This removes the need for the host to poll the QT1106 continuously.On each SPI transfer the host sends three bytes to theQT1106 and the QT1106 simultaneously sends three bytes to the host. The bytes sent from the host provide the QT1106with all its configuration information; the bytes sent from theQT1106 convey the key states.

Figure 1.1 All-Metal Slider and Wheel Construction

(downloadable example CAD files for wheels and sliders can be found on the Quantum website, http://www.qprox.com/toolbox , then click QT1106 )
Tips of triangles should be spaced <=4mm apart.<=4mm<=4mmSNSA3 SNSA2SNSA1 Position 0 Position 43Position 85 SNSA3SNSA3SNSA2SNSA1 0127 1 to 126Position (at 7 bits - 0 to 127)

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