QT240-ISSG

QT240-ISSG Datasheet

QT240-ISSG

Part	Datasheet
QT240-ISSG	QT240-ISSG (pdf)

PDF Datasheet Preview
QT240-ISSG 4 KEY QTOUCH SENSOR IC " Four independent charge-transfer ‘QT’ touch keys " Individual outputs per channel - active high " Projects prox fields through any dielectric " Sensitivity easily adjusted on a per-channel basis " 100% autocal for life - no adjustments required " 3.9V ~ 5.5V single supply operation " 10s, 60s, infinite autorecal timeout strap options " Sync pin for line sync to suppress noise " Spread spectrum operation " Pin options for auto recalibration timings " Extremely low cost per key " 20-SSOP RoHS compliant package SNS2 SNS2K SNS1 SNS1K OUT1 OUT2 OUT3 VSS SS/SYNC n.c. QT240 20-SSOP SNS3K SNS3 SNS4K SNS4 n.c. OSC VDD /RES OUT4 n.c. ! PC Peripherals ! Backlighted buttons ! Appliance controls ! Security systems ! Access systems ! Pointing devices ! Instrument panels ! Gaming machines The QT240 charge-transfer “QT’” QTouch IC is a self-contained digital sensor IC capable of detecting near-proximity or touch on four electrodes. It allows electrodes to project independent sense fields through any dielectric like glass, plastic, stone, ceramic, and wood. It can also turn metal-bearing objects into intrinsic sensors, making them responsive to proximity or touch. This capability coupled with its continuous self-calibration feature can lead to entirely new product concepts , adding high value to product designs. Each of the channels operate s independently of the others, and each can be tuned for a unique sensitivity level by simply changing its sample capacitor value. Two speeds are supported, one of which consumes on ly 90µA of typical current at 4V. Unique among capacitance sensors, the device incorporates spread -spectrum modulation for unsurpassed EMC compliance. The devices are designed specifically for human interfaces, like control panels, appliances, gaming devices, lighting controls, or anywhere a mechanical switch or button may be found they may also be used for some material sensing and control applications. These devices feature a SYNC pin which allows for synchronization with additional similar parts and/or to an external source to suppress interference. This pin doubles as a drive pin for spread-spectrum modulation. Option pins are provided which allow different timing and feature settings. The RISC core of these devices use signal processing techniques pioneered by Quantum which are designed to survive numerous real-world challenges, such as ‘stuck sensor’ conditions, component aging, moisture films, and signal drift. By using the charge-transfer principle, these devices deliver a level of performance clearly superior to older technologies yet are highly cost-effective. AVAILABLE OPTIONS TA -40oC to +85oC SSOP-20 QT240-ISSG Copyright 2003-2006 QRG Ltd QT240R R1.11/1006 Contents 1 Overview 3 Introduction 3 Operating Modes 3 Electrode Drive Wiring 3 Sensitivity 4 Introduction 4 Alternative Ways to Increase Sensitivity 4 Decreasing Sensitivity 4 Key Balance 4 2 QT240 Specifics 4 Signal Processing 4 Introduction 4 Drift Compensation 4 Threshold Level 5 Max On-Duration 5 Detection Integrator 5 Forced Sensor Recalibration 5 Fast Positive Recalibration 5 Options 5 Synchronization 6 3 Circuit Guidelines 6 Cs Sample Capacitor 6 Power Supply, PCB Layout 7 Oscillator Spread Spectrum 7 Unused Channels 7 ESD Protection 7 Crosstalk Precautions 7 4 Specifications 9 Absolute Maximum Specifications 9 Recommended Operating Conditions 9 AC Specifications 9 DC Specifications 9 Signal Processing 10 Mechanical Dimensions 10 Marking 11 Moisture Sensitivity Level MSL 11 Table Pin Listing - QT240-ISS Introduction QT240 devices are burst mode digital charge-transfer QT sensor ICs designed specifically for touch controls they include all hardware and signal processing functions necessary to provide stable sensing under a wide variety of conditions. Only a single low cost capacitor per channel is required for operation. Figures and show basic circuits for these device s. See Table for device pin listings. The devices employ bursts of charge-transfer cycles to acquire signals. Burst mode permits low power operation, dramatically reduces RF emissions, lowers susceptibility to RF fields, and yet permits excellent speed. Internally, signals are digitally processed to reject impulse noise using a 'consensus' filter that requires six consecutive confirmations of detection. The QT switches and charge measurement hardware functions are all internal to the device. A single-slope switched capacitor ADC includes the QT charge and transfer switches in a configuration that provides direct ADC conversion an external Cs capacitor accumulates the charge from sense-plate Cx, which is then measured. Larger values of Cx cause the charge transferred into Cs to rise more rapidly, reducing available resolution as a minimum resolution is required for proper operation, this can result in dramatically reduced gain. Larger values of Cs reduce the rise of differential voltage across it, increasing available resolution by permitting longer QT bursts. The value of Cs can thus be increased to allow larger values of Cx to be tolerated. The IC is responsive to both Cx and Cs, and changes in either can result in substantial changes in sensor gain. Unused channels If a channel is not used, a dummy sense capacitor nominal value 1nF of any type plus a 2.2K series resistor must be connected between unused SNS pin pairs, to ensure correct operation. Operating Modes The QT240 features spread-spectrum acquisition capability, external synchronization of acquire bursts, and fast and slow acquisition modes. These modes are enabled via high-value resistors connected to the SNS pins to ground or Vdd. These resistors are required in every circuit. There are two basic modes as shown in Figures and

PDF Datasheet Preview

QT240-ISSG
4 KEY QTOUCH SENSOR IC
" Four independent charge-transfer ‘QT’ touch keys " Individual outputs per channel - active high " Projects prox fields through any dielectric " Sensitivity easily adjusted on a per-channel basis " 100% autocal for life - no adjustments required " 3.9V ~ 5.5V single supply operation " 10s, 60s, infinite autorecal timeout strap options " Sync pin for line sync to suppress noise " Spread spectrum operation " Pin options for auto recalibration timings " Extremely low cost per key " 20-SSOP RoHS compliant package

SNS2 SNS2K

SNS1 SNS1K

OUT1 OUT2 OUT3

VSS SS/SYNC
n.c.

QT240
20-SSOP

SNS3K SNS3 SNS4K SNS4 n.c. OSC VDD /RES OUT4 n.c.
! PC Peripherals ! Backlighted buttons
! Appliance controls ! Security systems
! Access systems ! Pointing devices
! Instrument panels ! Gaming machines

The QT240 charge-transfer “QT’” QTouch IC is a self-contained digital sensor IC capable of detecting near-proximity or touch on four electrodes. It allows electrodes to project independent sense fields through any dielectric like glass, plastic, stone, ceramic, and wood. It can also turn metal-bearing objects into intrinsic sensors, making them responsive to proximity or touch. This capability coupled with its continuous self-calibration feature can lead to entirely new product concepts , adding high value to product designs.

Each of the channels operate s independently of the others, and each can be tuned for a unique sensitivity level by simply changing its sample capacitor value. Two speeds are supported, one of which consumes on ly 90µA of typical current at 4V. Unique among capacitance sensors, the device incorporates spread -spectrum modulation for unsurpassed EMC compliance.

The devices are designed specifically for human interfaces, like control panels, appliances, gaming devices, lighting controls, or anywhere a mechanical switch or button may be found they may also be used for some material sensing and control applications.

These devices feature a SYNC pin which allows for synchronization with additional similar parts and/or to an external source to suppress interference. This pin doubles as a drive pin for spread-spectrum modulation. Option pins are provided which allow different timing and feature settings.

The RISC core of these devices use signal processing techniques pioneered by Quantum which are designed to survive numerous real-world challenges, such as ‘stuck sensor’ conditions, component aging, moisture films, and signal drift.

By using the charge-transfer principle, these devices deliver a level of performance clearly superior to older technologies yet are highly cost-effective.

AVAILABLE OPTIONS

TA -40oC to +85oC

SSOP-20 QT240-ISSG

Copyright 2003-2006 QRG Ltd QT240R R1.11/1006

Contents
1 Overview 3 Introduction 3 Operating Modes 3 Electrode Drive Wiring 3 Sensitivity 4 Introduction 4 Alternative Ways to Increase Sensitivity 4 Decreasing Sensitivity 4 Key Balance 4
2 QT240 Specifics 4 Signal Processing 4 Introduction 4 Drift Compensation 4 Threshold Level 5 Max On-Duration 5 Detection Integrator 5 Forced Sensor Recalibration 5 Fast Positive Recalibration 5 Options 5 Synchronization 6
3 Circuit Guidelines 6 Cs Sample Capacitor 6 Power Supply, PCB Layout 7 Oscillator Spread Spectrum 7 Unused Channels 7 ESD Protection 7 Crosstalk Precautions 7
4 Specifications 9 Absolute Maximum Specifications 9 Recommended Operating Conditions 9 AC Specifications 9 DC Specifications 9 Signal Processing 10 Mechanical Dimensions 10 Marking 11 Moisture Sensitivity Level MSL 11

Table Pin Listing - QT240-ISS

Introduction

QT240 devices are burst mode digital charge-transfer QT sensor ICs designed specifically for touch controls they include all hardware and signal processing functions necessary to provide stable sensing under a wide variety of conditions. Only a single low cost capacitor per channel is required for operation.

Figures and show basic circuits for these device s. See Table for device pin listings.

The devices employ bursts of charge-transfer cycles to acquire signals. Burst mode permits low power operation, dramatically reduces RF emissions, lowers susceptibility to RF fields, and yet permits excellent speed. Internally, signals are digitally processed to reject impulse noise using a 'consensus' filter that requires six consecutive confirmations of detection.

The QT switches and charge measurement hardware functions are all internal to the device. A single-slope switched capacitor ADC includes the QT charge and transfer switches in a configuration that provides direct ADC conversion an external Cs capacitor accumulates the charge from sense-plate Cx, which is then measured.

Larger values of Cx cause the charge transferred into Cs to rise more rapidly, reducing available resolution as a minimum resolution is required for proper operation, this can result in dramatically reduced gain. Larger values of Cs reduce the rise of differential voltage across it, increasing available resolution by permitting longer QT bursts. The value of Cs can thus be increased to allow larger values of Cx to be tolerated. The IC is responsive to both Cx and Cs, and changes in either can result in substantial changes in sensor gain.

Unused channels If a channel is not used, a dummy sense capacitor nominal value 1nF of any type plus a 2.2K series resistor must be connected between unused SNS pin pairs, to ensure correct operation.

Operating Modes

The QT240 features spread-spectrum acquisition capability, external synchronization of acquire bursts, and fast and slow acquisition modes. These modes are enabled via high-value resistors connected to the SNS pins to ground or Vdd. These resistors are required in every circuit.

There are two basic modes as shown in Figures and

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Datasheet ID: QT240-ISSG 519366