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PDF AT42QT1010 Data sheet ( Hoja de datos )
| Número de pieza | AT42QT1010 | |
| Descripción | One-channel Touch Sensor IC | |
| Fabricantes | ATMEL Corporation | |
| Logotipo |  |
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Features
• Number of Keys:
– One
– Configurable as either a single key or a proximity sensor
• Technology:
– Patented spread-spectrum charge-transfer (direct mode)
• Key outline sizes:
– 6 mm x 6 mm or larger (panel thickness dependent); widely different sizes and
shapes possible
• Electrode design:
– Solid or ring electrode shapes
• PCB Layers required:
– One
• Electrode materials:
– Etched copper, silver, carbon, Indium Tin Oxide (ITO)
• Electrode substrates:
– PCB, FPCB, plastic films, glass
• Panel materials:
– Plastic, glass, composites, painted surfaces (low particle density metallic paints
possible)
• Panel thickness:
– Up to 12 mm glass, 6 mm plastic (electrode size and Cs dependent)
• Key sensitivity:
– Settable via capacitor (Cs)
• Interface:
– Digital output, active high
• Moisture tolerance:
– Good
• Power:
– 1.8V – 5.5V; 17 µA at 1.8V typical
• Package:
– 6-pin SOT23-6 RoHS compliant
– 8-pin UDFN/USON RoHS compliant
• Signal processing:
– Self-calibration, auto drift compensation, noise filtering
• Applications:
– Control panels, consumer appliances, proximity sensor applications, toys,
lighting controls, mechanical switch or button,
• Patents:
– QTouch® (patented charge-transfer method)
– HeartBeat™ (monitors health of device)
One-channel
Touch Sensor
IC
AT42QT1010
9541H–AT42–05/10
1 page  
AT42QT1010
2. Overview of the AT42QT1010
2.1 Introduction
The AT42QT1010 (QT1010) is a digital burst mode charge-transfer (QT™) sensor that is capable
of detecting near-proximity or touch, making it ideal for implementing touch controls.
With the proper electrode and circuit design, the self-contained digital IC will project a touch or
proximity field to several centimeters through any dielectric like glass, plastic, stone, ceramic,
and even most kinds of wood. It can also turn small metal-bearing objects into intrinsic sensors,
making them responsive to proximity or touch. This capability, coupled with its ability to
self-calibrate, can lead to entirely new product concepts.
The QT1010 is designed specifically for human interfaces, like control panels, appliances, toys,
lighting controls, or anywhere a mechanical switch or button may be found. It includes all
hardware and signal processing functions necessary to provide stable sensing under a wide
variety of changing conditions. Only a single low-cost capacitor is required for operation.
2.2 Basic Operation
Figure 1-1 on page 4 and Figure 1-1 on page 4 show basic circuits.
The QT1010 employs bursts of charge-transfer cycles to acquire its signal. Burst mode permits
power consumption in the microamp range, dramatically reduces RF emissions, lowers
susceptibility to EMI, and yet permits excellent response time. Internally the signals are digitally
processed to reject impulse noise, using a “consensus” filter which requires four consecutive
confirmations of a detection before the output is activated.
The QT switches and charge measurement hardware functions are all internal to the QT1010.
2.3 Electrode Drive
For optimum noise immunity, the electrode should only be connected to SNSK.
In all cases the rule Cs>>Cx must be observed for proper operation; a typical load capacitance
(Cx) ranges from 5-20 pF while Cs is usually about 2-50 nF.
Increasing amounts of Cx destroy gain, therefore it is important to limit the amount of stray
capacitance on both SNS terminals. This can be done, for example, by minimizing trace lengths
and widths and keeping these traces away from power or ground traces or copper pours.
The traces and any components associated with SNS and SNSK will become touch sensitive
and should be treated with caution to limit the touch area to the desired location.
A series resistor, Rs, should be placed in line with SNSK to the electrode to suppress ESD and
EMC effects.
2.4 Sensitivity
2.4.1
Introduction
The sensitivity on the QT1010 is a function of things like the value of Cs, electrode size and
capacitance, electrode shape and orientation, the composition and aspect of the object to be
sensed, the thickness and composition of any overlaying panel material, and the degree of
ground coupling of both sensor and object.
9541H–AT42–05/10
5
5 Page 
AT42QT1010
The HeartBeat indicator can be sampled by using a pull-up resistor on the OUT pin (Figure 3-6),
and feeding the resulting positive-going pulse into a counter, flip flop, one-shot, or other circuit.
The pulses will only be visible when the chip is not detecting a touch.
Figure 3-6.
Obtaining HeartBeat Pulses with a Pull-up Resistor (SOT23-6)
HeartBeat™ Pulses
VDD
5
Ro
1 VDD 3
OUT
SNSK
4
SNS
SYNC
VSS
2
6
If the sensor is wired to a microcontroller as shown in Figure 3-7 on page 11, the microcontroller
can reconfigure the load resistor to either Vss or Vdd depending on the output state of the
QT1010, so that the pulses are evident in either state.
Figure 3-7. Using a Microcontroller to Obtain HeartBeat Pulses in Either Output State (SOT23-6)
PORT_M.x
Ro
Microcontroller
1
OUT
3
SNSK
4
SNS
PORT_M.y
6
SYNC
3.9.3
Electromechanical devices like relays will usually ignore the short HeartBeat pulse. The pulse
also has too low a duty cycle to visibly affect LEDs. It can be filtered completely if desired, by
adding an RC filter to the output, or if interfacing directly and only to a high-impedance CMOS
input, by doing nothing or at most adding a small noncritical capacitor from OUT to Vss.
Output Drive
The OUT pin is active high and can sink or source up to 2 mA. When a large value of Cs
(>20 nF) is used the OUT current should be limited to <1 mA to prevent gain-shifting side
effects, which happen when the load current creates voltage drops on the die and bonding
wires; these small shifts can materially influence the signal level to cause detection instability.
9541H–AT42–05/10
11
11 Page | ||
| Páginas | Total 22 Páginas | |
| PDF Descargar | [ Datasheet AT42QT1010.PDF ] | |
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