QT111 Datasheet, PDF (4/6 Pages) Quantum Research Group – QT 11x Series Variations

Quantum Research Group Ltd.
4 August 2004
QT115-I / QT115H-I QProx™ 8-pin Sensor
See QT110 datasheet for primary information. This sheet only lists differences with the QT110.
This part is only available in -I suffix (-40..+85C)
Description
The QT115 is a variant of the QT110 having variable sensitivity and the ability to daisy-chain, allowing multiple
QT115's to be used in immediate proximity to each other to create a small touch panel of up to 10 keys. Like the
QT113, it has a variable threshold which can be modified by simply altering the value of the sample capacitor Cs,
which acts to modify gain. It does not include any of the option jumpers found on the QT110 or QT113; instead it
has a single option jumper for 'Master' or 'Slave' mode operation.
The QT115 includes 'Sync Out' and 'Sync In' pins for daisy-chaining. The first IC in the chain is the Master while
the remaining devices in the chain are slaves. Daisy-chaining lets each device take its turn in generating a burst,
free from interference by the other QT devices. In Master mode the IC operates autonomously, and generates a
20us negative Sync Out pulse on pin 3 after each burst. In Slave mode the IC issues a detection burst only after
it receives a negative Sync pulse on pin 4 from a prior device in the chain, which could be another Slave or a
Master. Slave devices in turn issue a 20us Sync pulse after each burst on pin 3.
The QT115 is designed for contact and prox sensing applications where high sensitivity is paramount, for
example when sensing through thick panels or windows or for security monitoring. The QT115 trades off power
consumption for speed and sensing range. Also, note that the device has a consensus filter count of 3 instead of
4, and does not have the drive capability for a piezo 'beeper'.
If desired, the Master device can be eliminated and the chain of Slave devices can be mastered from an external
pulse source of 20us negative pulses at the desired repetition rate. This potentially allows for faster operation.
Differences with the QT110
The QT115 IC is exactly the same in all respects to the QT110 with the following exceptions (refer to Tables 5.2,
5.3, 5.4, and 5.5 in the QT110 datasheet).
5.2 RECOMMENDED OPERATING CONDITIONS
Cx Load Capacitance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 to 100pF
Cs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10nF to 500nF
5.3 AC SPECIFICATIONS VDD = 3.0, TA = RECOMMENDED OPERATING RANGE
Parameter
Description
Min
Typ
Max
Units
Notes
TBS1
Burst spacing interval, master
30
40
ms Cs = 10nf to 500nf, Cx = 0
TBS2
Burst spacing interval, slave
2
ms Cs = 10nf, Cx = 0
TBL
Burst length
0.5
75
ms Cs = 10nf to 500nf, Cx = 0
TR
Response time
8
300
Note 1: Lengthens with increasing Cs but decreases with increasing Cx; see Chart 3.
ms Note 1
5.4 SIGNAL PROCESSING
Description
Threshold differential, fixed
Hysteresis
Consensus filter length
Positive drift compensation rate
Negative drift compensation rate
Post-detection recalibration timer duration
Min Typ Max
6
17
3
1,800
40
10
Units
counts
%
samples
ms/level
ms/level
secs
Notes
Note 1
w.r.t. threshold cts.
Note 1: All percentage thresholds have been eliminated and replaced with a fixed threshold w.r.t. the reference level
QT113 QProx™ 8-pin Sensor
© 1999 QRG Ltd.