QT112-IS Atmel, QT112-IS Datasheet - Page 6

• Manufacturer Part Number: QT112-IS
• Description: SENSOR IC TOUCH/PROXMTY 1CH8SOIC
• Manufacturer: Atmel
• Series: QProx™r
• Type: Capacitiver

Specifications of QT112-IS

• Rohs Status: RoHS non-compliant
• Touch Panel Interface: 1, 2-Wire
• Number Of Inputs/keys: 1 Key
• Resolution (bits): 14 b
• Data Interface: Serial
• Voltage Reference: Internal
• Voltage - Supply: 2.45 V ~ 5.25 V
• Current - Supply: 60µA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Output Type: Logic
• Interface: 2-Wire
• Input Type: Logic
• Package / Case: -
• Other names: 427-1008

4 August 2004
Quantum Research Group Ltd.
Calibration and Drift Compensation
Calibration and drift compensation operate similarly to the QT110. With large values of Cs and small values of
Cx, drift compensation will appear to operate more slowly than with the reverse. Note that the positive and
negative drift compensation rates are different; the sensor will compensate more quickly for the removal of an
object than it will to the introduction of an object.
The QT115 uses a fixed recalibration timeout of 10 seconds.
Response Time
The QT115's response time is entirely dependent on the burst rate. In Master mode the nominal burst rate is
40ms, and 3 successive bursts are required to confirm a detection, giving a nominal 120ms response time.
In slave mode, the burst rate and hence response time are dependent on the input sync pulse rate. Faster sync
pulse rates will lead to faster response times.
HeartBeat™ Signal
The QT115's HeartBeat pulse works exactly the same as in the QT110 except that the HeartBeat rate is the
same as the burst rate. In Master mode, the HeartBeat signal occurs just before the acquisition burst. In slave
mode, it occurs just after receipt of the slave pulse on pin 4. As with the QT110, the HB signal can be
suppressed if not wanted by a variety of simple methods.
Notes on Daisy Chaining QT115's
The QT115 is intended to be daisy-chained for the purpose of allowing each of the sensors to operate without
interference from other devices in the chain. This allows electrodes from each device to be placed immediately
adjacent the other electrodes with only the barest of gaps.
Individual devices in the chain can have unique sensitivities. QT113-style sensing allow for very high sensitivity
levels if required. One device can be used with a large metal area to create a prox detector capable of many
centimeters range, for example to activate the panel, equipment, or a light upon a mere hand-wave. The other
devices in the chain can be used to implement low-gain touch switches that must be contacted by a fingertip for
activation. The net effect of this configuration can be quite dramatic.
The only limitation is that the sum of the burst lengths, which depends on load Cx and the Cs capacitor, must not
be so long that burst of the last device in the chain overlaps the burst of the first device. Should this occur, the
first and last devices may interfere with each other if the electrodes and wiring are adjacent to each other. One
simple solution to this problem is to physically separate the traces and electrodes from devices that have
overlapping bursts.
QT115H Version
The QT115H version is the same as the QT115 except with an active-high output.
Package Marking - QT115
DIP Package: DIP devices are marked 'QT115'
SO8 Package: Marked 'QT1 H' or ‘QT115 I’
Package Marking - QT115H
DIP Package: DIP devices are marked 'QT115H'
SO8 Package: Marked 'QT1 L'
QT113 QProx™ 8-pin Sensor
© 1999 QRG Ltd.