Creates `touch buttons' through dielectric Only inexpensive capacitor
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4-KEY CHARGE-TRANSFER
Creates `touch buttons' through dielectric Only inexpensive capacitor required Simple matrix geometry 100% drift compensation lifetime reliability rollover: senses keys same time Back-lit keys possible with electrodes Simple direct 'per key' active-high drive outputs Auto recalibration after seconds touch single power supply operation CMOS design very power consumption 14-pin SOIC package E604 Evaluation reference design board available
OPT1 OPT2
QMatrixQT60040
APPLICATIONS Security keypanels Industrial keyboards Appliance controls Vandal-proof keypads Amachines Touch-screens Automotive controls peripheral controls
QT60040 digital charge-transfer ("QT") QMatrixIC designed detect touch keys scanned matrix. will project keys through almost dielectric, like glass, plastic, stone, ceramic, even most kinds wood, thicknesses 6mm. touch areas defined simple 2-part interdigitated electrodes conductive material, like copper, Indium-Tin-Oxide (ITO), screened silver carbon deposited rear control panel. Alternatively keys implemented stick-on flex circuit that adhered rear most panels. designed specifically domestic appliances, computer peripheral control buttons, Amachines, security panels, portable instruments, machine tools, similar products that subject environmental challenges physical attack. permits construction 100% sealed, watertight keypanels that immune environmental factors such humidity condensation, temperature, dirt accumulation, physical deterioration panel surface from abrasion, chemicals, abuse. QT60040 contains Quantum-pioneered self-calibration, drift compensation, digital filtering algorithms that make sensing function extremely robust survivable. device easily control keys over graphical panels LEDs when used with clear, conductive electrodes. does require 'chip glass' other exotic fabrication techniques, thus allowing source keymatrix from multiple vendors. External circuitry consists only single, inexpensive capacitor. sensitivity keys simply changing value this capacitor. device outputs which indicate detection keys; keys sensed time. QT60040 features automatic recalibration timeouts which will cause device recalibrate keys individual basis when they 'stuck intervals either 60s, depending jumper option. QT60040 technology makes important variant charge-transfer sensing, transverse charge-transfer, format that minimizes number required scan lines external components. Unlike older technologies does require key, cost competitive even with some rubber membrane technologies. distinct advantage accelerated time market fact that custom molded membranes required; entire system designed using common materials. E604 board available from Quantum reference design that permits full evaluation QT60040.
AVAILABLE OPTIONS SOIC +700C QT60040-S -400C +850C QT60040-IS
QT60040-D
Copyright 2000 Quantum Research Group R1.02/0901
Quantum Research Group
OVERVIEW
QT60040 CMOS charge-transfer (QT) sensor designed specifically matrix touch controls; includes signal processing functions necessary provide stable sensing under wide variety changing conditions. Only cost external capacitor required operation. QT60040 uses burst-mode charge transfer methods pioneered patented Quantum. This revolutionary technology
CIRCUIT MODEL
electrical circuit model shown Figure 1-4. coupling capacitance across electrodes from each finger represented Cx1, Cx2a, Cx2b. sampling capacitor used accumulate charge during course burst. important parasitic capacitance from line ground, Cx3, also shown. switch timing action shown Figure 1-5. Initially, switch closed reset then re-opened. After opened, closed charge capacitances associated with Y-line, including Y-to-X capacitances. After closed, four lines raised high, that there then zero differential potential from selected line line. Then, opened closed, causing charge flow from capacitances into charges slightly with polarity shown. Then selected line driven low, causing step-function decrease charge whose magnitude proportionate amount coupling from final charge accumulated cycle thus direct function minus small amount charge subtracted Cx2a Cx2b Cfinger network. Since charge from Cx2a Cx2b network highly dependent Cfinger, which effectively forms capacitive divider, total charge absorbed dependent touch: touch nets more charge transferred into cycle because less charge transferred cycle. acquisition process controlled state machine which continues acquisition cycle burst, which finally terminates when voltage across reaches predefined level Vref. This burst takes hundreds even thousands cycles complete;
Figure Field flow between elements
overlying panel
element cmos driver
element
allows construction entirely forms keypanels which include back-illumination, arbitrary shapes keys, 'morphed' keys wrapped onto complex surfaces, keys having unique textures feel, very cost. QT60040 uses matrix, having drive lines receive line. This configuration reduces interconnect requirements also lowers external component count charge sampling capacitor which sequentially shared four keys. QT60040 four simple active-high CMOS outputs that high when corresponding touched. keys touched same time; three more keys touched will limit first touch outputs. option allows this restricted only desired. device operates regulated power supply which from common 78L05-type regulator simple 2-stage zener regulator supply.
Figure Field Flows When Touched
rlyin
FIELD FLOWS
Figure shows charge transferred across electrode permeate overlying panel material; this charge flow exhibits rapid dQ/dt during edge transitions drive pulse. charge emitted electrode partly received onto electrode which then captured capacitor processed. QT60040 matrix uses edge-driven rows sense column detect keys. drive occurs burst pulses each key. charge flows into motion drive signals partially absorbed touch human finger (Figure 1-2) resulting decrease coupling from coupled charge increases presence conductive film like water (Figure 1-3) which acts bridge elements. Increasing signals water films quite easy discern detected QT60040.
element
elem
driver
Figure Fields With Conductive Film
film
Figure QT60040 Circuit Model
Figure Conversion Single Electrodes
QT60040
CFINGER CX2A CX2B
DRIVE Vref
RESET CHARGE TRANSFER
STATE MACHINE DONE START RESULT
coupling tracks PCB; traces from intersections these capacitors solid touch pads which implemented metallizations rear control panel. Touching front panel same absorptive effect signal strength interdigitated electrode set. values Cx2a Cx2b should consistent among keys preserve signal balance, which required proper operation. surface area geometry this type electrode should adjusted suit desired activation area. Typical values Cx2a Cx2b range from 10pF. traces leading from junctions these capacitors solid touch pads should load more than 10pF, thus traces these pads should thin short accompanied ground plane other traces.
POST PROCESSOR
OPTIONS
Figure Circuit Switch Timings
INTERDIGITATED ELECTRODES
electrodes made using interdigitated sets fingers, serpentines, spirals similar patterns (Figure 1-7). element each must connected line, with other connected common line. pattern surface area should similar from preserve relative sensitivities. important prevent substantial capacitive coupling from `bare' line finger. transient increase will cause sudden disturbance common keys that create unintentional detections. connecting trace running between keys should thin possible, side flex circuit away from user panel, where possible closely parallel with segment nearby trace suppress this effect. problem bare line demonstrated touching capacitor (which connected which will cause random keys activate with each touch. cases where possible have both traces same plane, traces should `finger' side board. cases where lines opposite planes, substrate flex circuit, pcb) should thin
ycle
burst length depends value capacitances, Cfinger. Increasing increases burst length, increasing decreases burst length, increasing increase burst length. Increasing Cfinger decreases burst length. value burst length thus variable that dependent these capacitances; burst length used create internal reference signal level during calibration cycle, determine presence touch virtue change burst length relative reference level. Because capacitor shared among four channels important that four interdigitated designs reasonably well matched. also important keep minimum while maximizing values Cx2a Cx2b through good design methods. These requirements also dictate that placed close keys achieve good sensitivity levels; long traces also increase risk susceptibility interference, well gain. reduce Cx3, line should close other unrelated traces over near ground planes.
Figure Sample Electrode Geometries
SINGLE ELECTRODE OPERATION
alternative mode operation shown Figure 1-6. Capacitances Cx2a Cx2b implemented discrete capacitances, possibly using intentional mutual capacitive
PARALLEL LINES SERPENTINE SPIRAL
possible promote equal field coupling through overlying panel material increase sensitivity. Suggested design rules interdigitated keys shown Figure 1-8. Note small `tails' which along exposed line between keys provide shielding against Y-only finger touches over electrode set, narrow common line, which combination suppress Y-only touch detection desribed above.
either seconds continuous detection jumper option (Table 2-1); this option applies keys. On-duration interaction among keys; timeout will have effect another key.
1.5.5 DETECTION INTEGRATOR
suppress false detections caused spurious events like electrical noise, QT60040 incorporates detection integration counter that increments with each detection sample until limit reached, which point detection confirmed. detection sensed samples prior final count, counter reset immediately zero, forcing process restart. required count samples key.
SIGNAL PROCESSING
QT60040 calibrates processes signals using number algorithms pioneered Quantum. These algorithms specifically designed survive most environmental conditions.
1.5.1 SELF-CALIBRATION
QT60040 fully self-calibrating. powerup scans matrix sets appropriate calibration points each. special operator factory calibration circuit tweak required bring keys into operation. self calibration procedure typically requires second complete.
1.5.2 DRIFT COMPENSATION ALGORITHM
Signal drift occur because changes over time. crucial that drift compensated for, otherwise false detections, non-detections, sensitivity shifts will follow. Drift compensation (Figure 1-9) performed making reference level track signal slow rate, only while there detection effect. rate adjustment performed slowly, otherwise legitimate detections might ignored. QT60040 drift compensates using slew-rate limited change reference level; threshold hysteresis values slaved this reference. QT60040's drift compensation 'asymmetric': drift-compensation occurs direction faster than does other. Specifically, compensates faster decreasing loads. Increasing loads (more contact with object, which results decreasing signal) should compensated slowly, that sensitivity approaching finger affected. Removal object compensated faster rate allow sensor recover quickly prepare next valid touch.
Figure Design Rules
18x18mm size
0.75mm gaps 0.5mm lines
shield tails
1.5.3 THRESHOLD HYSTERESIS CALCULATIONS
threshold value established offset reference level. drift over time, reference drift compensates with changes threshold level automatically recomputed real time that never error. Since touches result negative signal swings, threshold below signal reference level. QT60040 employs hysteresis delta between reference threshold levels. signal must rise distance from threshold reference before detection event drops registers untouched.
Common Line
1.5.4 ON-DURATION
foreign object contacts signal change enough create detection lasting duration contact. overcome this, part includes individual timers which monitor detection duration. detection exceeds timer limit setting, sensor will perform full recalibration. This known On-Duration feature. After On-Duration interval expired recalibration taken place, will once again function normally even still contact with foreign object, best ability. On-Duration
Figure Drift Compensation
Reference Hysteresis Threshold Signal Output
Figure Basic Circuit Diagram
OPTIONS Opt1 Opt2 KEYS
OPT2 used calibration time-out function. OPT2 connected ground, keys will time recalibrate after seconds continuous detection key. OPT2 left open connected Vdd, keys will recalibrate after seconds. either case keys will continue functional after time-out, increased amounts finger touch.
POWER SUPPLY
uses power supply rail internal reference voltage. power supply shared with another electronic system, care should taken assure that supply free digital spikes, sags, surges which adversely affect circuit. QT60040 will track slow changes Vcc, adversely affected rapid voltage steps impulse noise supply rail. power supply range from volts, should regulated standard regulator such 78L05 type. cases where cost objective, possible double-zener regulation.
ACTIVE-HIGH OUTPUTS
QT60040
proper operation 100nF (0.1uF) ceramic bypass capacitor should used between Vss; bypass should placed very close device's power pins.
OUTPUTS
CIRCUIT SPECIFICS
basic QT60040 circuit shown Figure 2-1.
CAPACITOR
QT60040 requires only single external sampling capacitor (Cs) operate. This capacitor should have good stability characteristics. possible optimal type capacitor, best stability plastic type such polyester film should used. Increasing values will result increased sensitivity, much sensitivity also result spurious operation. optimal value will depend type panel material, thickness, geometry; experimentation required determine proper value. Typical suitable values range from 22nF 220nF; 47nF good value start from most cases.
device four active-high outputs, sensing channel, which indicate touch. These outputs should used logic-level switching only should drive loads more than 1mA. High loads cause shifts device rails which lead spurious operation.
PROTECTION
general QT60040 will protected from direct static discharge overlying panel. However, even with panel, transients still flow into electrode induction, extreme cases, dielectric breakdown. Porous thin materials allow spark tunnel right through panel material. Testing required reveal problems. QT60040 does have diode protection terminals which absorb protect device from most induced discharges, 20mA; usefulness internal clamping will depend dielectric properties, panel thickness, rise time transients, their duration. device pins further protected inserting series resistance into lines. resistances chosen should high interfere with process. Every board layout different thus difficult specify suitable value, however, typical values will range from ohms ohms. serious cases additional low-capacitance high-conductance clamp diodes (e.g. BAV99) added shunt aside from pins power ground rails. QT60040's drive lines always being driven impedance; they never 3-state unless circuit just powering powered down. This considerable advantage dealing with ESD. output pins also vulnerable should resistor and/or diode protected they danger being subject ESD.
OPTION PINS
There option pins whose function shown Table 2-1. OPT1 used rollover option. this connected ground, will only sense time. OPT1 left open connected Vdd, sense keys simultaneously will suppress additional keys.
Table Option Functions
OPT1 OPT2 keys sensed only sensed seconds recalibration seconds recalibration
Figure E604 Schematic
CONN2
CONN2
J3:1 J3:2 J3:3 J3:4 J3:5 J3:6 Vunreg J3:7 J3:8 2N4401
Rollover Recal Timeout
OPT1
OPT2
47nF
QT60040
2N4401
2N4401
2N4401
LM78L05ACZA
1N4001
4.7uF/16V 22uF/6.3V
RS1:2
RS1:4
RS1:3
RS1:1
Figure E604 Layers
INTERFACE
POWER
2000 Ltd.
BATTERY
RESEARCH GROUP
Layer
Bottom Layer
Silk Layer
WWW.QPROX.COM ADMIN@QPROX.COM
E604 4-KEY MATRIX BOARD
ABSOLUTE MAXIMUM SPECIFICATIONS
Operating temp designated suffix Storage temp -55OC +125OC -0.5 +6.0V continuous current, control drive ±20mA Short circuit duration ground, infinite Short circuit duration VDD, infinite Voltage forced onto -0.6V (Vdd 0.6) Volts
RECOMMENDED OPERATING CONDITIONS
+4.50 5.25V Supply ripple+noise 10mV value 22nF 220nF Output load ±1mA
SPECIFICATIONS
5.0V, 47nF, recommended range, unless otherwise noted
Parameter
Description
Supply current input logic level High input logic level output voltage High output voltage Input leakage current Acquisition resolution
0.65
Units
Notes
Vdd-0.7
bits
sink source
SPECIFICATIONS
5.0V, 47nF, recommended range, unless otherwise noted. Test circuit Figure
Parameter
Description
Response time Sensitivity Sample frequency Burst spacing Power-up delay operate
Units
Notes
geometry dependent
secs
SIGNAL PROCESSING
Parameter
Description
Detection integrator counts On-Duration Threshold, from reference Hysteresis Drift rate, negative Drift rate, positive Recalibration duration
Units
counts counts counts
Notes
±20%, option selectable
counts signal threshold
0.25
counts secs
ORDERING INFORMATION
PART
QT60040-D QT60040-S QT60040-IS
TEMP RANGE
PACKAGE
PDIP-14 SOIC-14 SOIC-14
MARKING
QT60040 QT60040 QT60040
DUAL IN-LINE PACKAGE
indicator
Base level Seating level
SYMBOL
7.112 7.874 15.24 18.8 1.78 0.36 1.14 2.54 2.92 0.38 3.18 3.56 7.874 8.128 0.20
Package Type: Dual-in-Line Millimeters Notes 7.493 8.382 15.24 19.3 2.03 0.56 1.78 2.54 3.68 3.43 4.32 7.874 9.906 0.38 0.28 0.31 0.74 0.07 0.014 0.045 0.100 0.115 0.015 0.125 0.14 0.31 0.32 0.008
Inches 0.295 0.33 0.76 0.08 0.022 0.070 0.100 0.145 0.135 0.17 0.31 0.39 0.015
Notes
Typical
Typical
Typical
Typical
SMALL OUTLINE PACKAGE
Seating level Base level
SYMBOL
8.56 5.79 3.81 1.35 0.10 1.27 0.36 0.41 0.20 0.25
Package Type: SOIC Millimeters Notes 8.81 6.20 3.99 1.75 0.25 1.27 0.51 1.27 0.25 0.51 0.337 0.228 0.150 0.31 0.004 0.050 0.014 0.016 0.008 0.014
Inches 0.347 0.244 0.157 0.33 0.010 0.050 0.020 0.050 0.010 0.020
Notes
Quantum Research Group
Holiday Drive Bldg. Pittsburgh, 15220 Tel: 412-391-7367 Fax: 412-291-1015 admin@qprox.com
©2001 Ltd.
Patented worldwide patents pending
http://www.qprox.com
United Kingdom Enterprise House, Southampton, Hants SO14 Tel: (0)23 8045 3934 Fax: (0)23 8045 3939
This device expressly medical human safety related application without express written consent officer company.
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