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QT118H-IS Schematic ( PDF Datasheet ) - ETC

Teilenummer QT118H-IS
Beschreibung CHARGE-TRANSFER TOUCH SENSOR
Hersteller ETC
Logo ETC Logo 




Gesamt 13 Seiten
QT118H-IS Datasheet, Funktion
lQ
QProxQT118H
CHARGE-TRANSFER TOUCH SENSOR
Less expensive than many mechanical switches
Projects a ‘touch button’ through any dielectric
Turns small objects into intrinsic touch sensors
100% autocal for life - no adjustments required
Only one external part required - a 1¢ capacitor
Piezo sounder direct drive for ‘tactile’ click feedback
LED drive for visual feedback
3V 20µA single supply operation
Toggle mode for on/off control (strap option)
10s or 60s auto-recalibration timeout (strap option)
Pulse output mode (strap option)
Gain settings in 3 discrete levels
Simple 2-wire operation possible
HeartBeat™ health indicator on output
Vdd
Out
O pt1
O pt2
1
2
3
4
8 Vss
7 Sns2
6 Sns1
5 Gain
APPLICATIONS -
Light switches
Industrial panels
Appliance control
Security systems
Access systems
Pointing devices
Elevator buttons
Toys & games
The QT118H charge-transfer (“QT’”) touch sensor is a self-contained digital IC capable of detecting near-proximity or touch. It will
project a sense field through almost any dielectric, like glass, plastic, stone, ceramic, and most kinds of wood. It can also turn
small metal-bearing objects into intrinsic sensors, making them respond to proximity or touch. This capability coupled with its
ability to self calibrate continuously can lead to entirely new product concepts.
It is designed specifically for human interfaces, like control panels, appliances, toys, lighting controls, or anywhere a mechanical
switch or button may be found; it may also be used for some material sensing and control applications provided that the presence
duration of objects does not exceed the recalibration timeout interval.
The IC requires only a common inexpensive capacitor in order to function. A bare piezo beeper can be connected to create a
‘tactile’ feedback clicking sound; the beeper itself then doubles as the required external capacitor, and it can also become the
sensing electrode. An LED can also be added to provide visual sensing indication. With a second inexpensive capacitor the device
can operated in 2-wire mode, where both power and signal traverse the same wire pair to a host. This mode allows the sensor to
be wired to a controller with only a twisted pair over a long distances.
Power consumption is under 20µA in most applications, allowing operation from Lithium cells for many years. In most cases the
power supply need only be minimally regulated.
The IC’s RISC core employs signal processing techniques pioneered by Quantum; these are specifically designed to make the
device survive real-world challenges, such as ‘stuck sensor’ conditions and signal drift. Even sensitivity is digitally determined and
remains constant in the face of large variations in sample capacitor Cs and electrode Cx. No external switches, opamps, or other
analog components aside from Cs are usually required.
The device includes several user-selectable built in features. One, toggle mode, permits on/off touch control, for example for light
switch replacement. Another makes the sensor output a pulse instead of a DC level, which allows the device to 'talk' over the
power rail, permitting a simple 2-wire interface. The Quantum-pioneered HeartBeat™ signal is also included, allowing a host
controller to monitor the health of the QT118H continuously if desired. By using the charge transfer principle, the IC delivers a
level of performance clearly superior to older technologies in a highly cost-effective package.
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AVAILABLE OPTIONS
TA
00C to +700C
-400C to +850C
SOIC
QT118H-S
QT118H-IS
8-PIN DIP
QT118H-D
-
©1999-2000 Quantum Research Group
R1.03 / 0302






QT118H-IS Datasheet, Funktion
break into high frequency oscillation, get hot, and stop
working.
Option strap configurations are read by the QT118H only on
powerup. Configurations can only be changed by powering
the QT118H down and back up again; a microcontroller can
directly alter most of the configurations and cycle power to
put them in effect.
2.2 OUTPUT FEATURES
The QT118H is designed for maximum flexibility and can
accommodate most popular sensing requirements. These
are selectable using strap options on pins OPT1 and OPT2.
All options are shown in Table 2-1.
2.2.1 DC MODE OUTPUT
The output of the device can respond in a DC mode, where
the output is active-high upon detection. The output will
remain active for the duration of the detection, or until the
Max On-Duration expires, whichever occurs first. If the latter
occurs first, the sensor performs a full recalibration and the
output becomes inactive until the next detection.
In this mode, two Max On-Duration timeouts are available:
10 and 60 seconds.
2.2.2 TOGGLE MODE OUTPUT
This makes the sensor respond in an on/off mode like a flip
flop. It is most useful for controlling power loads, for
example in kitchen appliances, power tools, light switches,
etc.
Max On-Duration in Toggle mode is fixed at 10 seconds.
When a timeout occurs, the sensor recalibrates but leaves
the output state unchanged.
2.2.3 PULSE MODE OUTPUT
This generates a positive pulse of 75ms duration with every
new detection. It is most useful for 2-wire operation (see
Figure 1-2), but can also be used when bussing together
several devices onto a common output line with the help of
steering diodes or logic gates, in order to control a common
load from several places.
Max On-Duration is fixed at 10 seconds if in Pulse output
mode.
2.2.4 HEARTBEATOUTPUT
The output has a full-time HeartBeat™ ‘healthindicator
superimposed on it. This operates by taking 'Out' into a
3-state mode for 350µs once before every QT burst. This
output state can be used to determine that the sensor is
operating properly, or, it can be ignored using one of several
simple methods.
Since Out is normally low, a pullup resistor will create
positive HeartBeat pulses (Figure 2-3) when the sensor is
not detecting an object; when detecting an object, the output
will remain active for the duration of the detection, and no
HeartBeat pulse will be evident.
If the sensor is wired to a microcontroller as shown in Figure
2-4, the controller can reconfigure the load resistor to either
ground or Vcc depending on the output state of the device,
so that the pulses are evident in either state.
Electromechanical devices will usually ignore this short
pulse. The pulse also has too low a duty cycle to visibly
activate LEDs. It can be filtered completely if desired, by
adding an RC timeconstant to filter the output, or if
interfacing directly and only to a high-impedance CMOS
input, by doing nothing or at most adding a small non-critical
capacitor from Out to ground (Figure 2-5).
2.2.5 PIEZO ACOUSTIC DRIVE
A piezo drive signal is generated for use with a bare piezo
sounder immediately after a detection is made; the tone lasts
for a nominal 75ms to create a tactile feedbacksound.
The sensor will drive most common bare piezo beepers
directly using an H-bridge drive configuration for the highest
possible sound level at all supply voltages; H-bridge drive
effectively doubles the supply voltage across the piezo. The
piezo is connected across pins SNS1 and SNS2. This drive
operates at a nominal 4kHz frequency, a common resonance
point for enclosed piezo sounders. Other frequencies can be
obtained upon special request.
If desired a bare piezo sounder can be directly adhered to
the rear of a control panel, provided that an acoustically
resonant cavity is also incorporated to give the desired
sound level.
Since piezo sounders are merely high-K ceramic capacitors,
the sounder will double as the Cs capacitor, and the piezo's
Figure 2-3
Getting HB pulses with a pulup resistor when not active
Figure 2-4
Using a micro to obtain HB pulses in either output state
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QT118H-IS pdf, datenblatt
SYMBOL
a
A
M
m
Q
P
L
L1
F
R
r
S
S1
Aa
x
Y
Min
6.096
7.62
9.017
7.62
0.889
0.254
0.355
1.397
2.489
3.048
0.381
3.048
-
7.62
8.128
0.203
Package type: 8pin Dual-In-Line
Millimeters
Max
Notes
Min
7.112
8.255
10.922
7.62
-
-
0.559
1.651
2.591
3.81
-
3.556
4.064
7.062
9.906
0.381
Typical
BSC
Typical
BSC
0.24
0.3
0.355
0.3
0.035
0.01
0.014
0.055
0.098
0.12
0.015
0.12
-
0.3
0.32
0.008
Inches
Max
0.28
0.325
0.43
0.3
-
-
0.022
0.065
0.102
0.15
-
0.14
0.16
0.3
0.39
0.015
Notes
Typical
BSC
Typical
BSC
SYMBOL
M
W
Aa
H
h
D
L
E
e
ß
Ø
Min
4.800
5.816
3.81
1.371
0.101
1.27
0.355
0.508
0.19
0.381
Package type: 8pin SOIC
Millimeters
Max
Notes
Min
4.979
6.198
3.988
1.728
0.762
1.27
0.483
1.016
0.249
0.762
BSC
0.189
0.229
0.15
0.054
0.004
0.050
0.014
0.02
0.007
0.229
Inches
Max
0.196
0.244
0.157
0.068
0.01
0.05
0.019
0.04
0.01
0.03
Notes
BSC
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11

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