AT42QT1012-TSHR Atmel, AT42QT1012-TSHR Datasheet - Page 5

• Manufacturer Part Number: AT42QT1012-TSHR
• Description: IC TOUCH SENSOR 1KEY SOT23-6
• Manufacturer: Atmel
• Series: QTouch™r
• Type: Capacitiver

Specifications of AT42QT1012-TSHR

• Touch Panel Interface: 1, 2-Wire
• Number Of Inputs/keys: 1 Key
• Resolution (bits): 9, 14 b
• Data Interface: Serial
• Voltage Reference: Internal
• Voltage - Supply: 1.8 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-6
• Output Type: Logic
• Interface: Digital
• Input Type: Logic
• Supply Voltage: 1.8 V to 5.5 V
• Dimensions: 2.9 mm L x 1.6 mm W x 1.45 mm H
• Output Voltage: 0.6 V to 0.7 V
• Temperature Range: - 40 C to + 85 C
• Termination Style: SMD/SMT
• Supply Current: 31.5µA
• Supply Voltage Range: 1.8V To 5.5V
• Sensor Case Style: SOT-23
• No. Of Pins: 6
• Operating Temperature Range: -40°C To +85°C
• Svhc: No SVHC (15-Dec-2010)
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: AT42QT1012-TSHRTR

2. Overview of the AT42QT1012
2.1
2.2
2.3
9543D–AT42–08/10
Introduction
Basic Operation
Electrode Drive
The AT42QT1012 (QT1012) is a single key device featuring a touch on/touch off (toggle) output
with a programmable auto switch-off capability.
The QT1012 is a digital burst mode charge-transfer (QT
controls. It includes all hardware and signal processing functions necessary to provide stable
sensing under a wide variety of changing conditions; only low cost, noncritical components are
required for operation. With its tiny low-cost packages, this device can suit almost any product
needing a power switch or other toggle-mode controlled function, especially power control of
small appliances and battery-operated products.
A unique “green” feature of the QT1012 is the timeout function, which can turn off power after a
time delay.
Like all QTouch
and spread-spectrum burst modulation in order to provide for the most reliable touch sensing
possible.
Figure 1-1 on page 3
devices.
The QT1012 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 QT1012.
Figure 2-1 on page 6
For optimum noise immunity, the electrode should only be connected to the SNSK pin.
In all cases the sample capacitor Cs should be much larger than the load capacitance (Cx).
Typical values for Cx are 5 – 20 pF while Cs is usually 2.2 – 50 nF.
Note:
Increasing amounts of Cx destroy gain, therefore it is important to limit the amount of load
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.
To endure that the correct output mode is selected at power-up, the OUT trace should also be
carefully routed.
Cx is not a physical discrete component on the PCB, it is the capacitance of the touch
electrode and wiring. It is show in
equivalent circuit.
™
devices, the QT1012 features automatic self-calibration, drift compensation,
shows the sense electrode connections (SNS, SNSK) for the QT1012.
and
Figure 1-2 on page 4
Figure 2-1 on page 6
show basic circuits for the 6-pin and 8-pin
™
) sensor designed specifically for touch
to aid understanding of the
AT42QT1012
5