lQ
C
HARGE
-T
RANSFER
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OUCH
S
ENSOR
QProx鈩?QT118H
Less expensive than many mechanical switches
Projects a 鈥榯ouch button鈥?through any dielectric
Turns small objects into intrinsic touch sensors
100% autocal for life - no adjustments required
Only one external part required - a 1壟 capacitor
Piezo sounder direct drive for 鈥榯actile鈥?click feedback
LED drive for visual feedback
3V 20碌A(chǔ) single supply operation
碌
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鈩?health indicator on output
Vdd
O ut
O pt1
O pt2
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Vss
Sn s2
Sn s1
G ain
Q T1 18 H
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APPLICATIONS -
Light switches
Industrial panels
Appliance control
Security systems
Access systems
Pointing devices
Elevator buttons
Toys & games
The QT118H charge-transfer (鈥淨(jìng)T鈥欌€? 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
鈥榯actile鈥?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 20碌A(chǔ) in most applications, allowing operation from Lithium cells for many years. In most cases the
power supply need only be minimally regulated.
The IC鈥檚 RISC core employs signal processing techniques pioneered by Quantum; these are specifically designed to make the
device survive real-world challenges, such as 鈥榮tuck sensor鈥?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鈩?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.
0 C to +70 C
-40
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C to +85
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T
A
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AVAILABLE OPTIONS
SOIC
QT118H-S
QT118H-IS
8-PIN DIP
QT118H-D
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lq
漏1999-2000 Quantum Research Group
R1.03 / 0302
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