lQ
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Patented charge-transfer (‘QT’) design
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Ten independent QT sensing fields (keys)
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2.8V ~ 5.5V single supply operation
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40µA current typ @ 3V in 360ms LP mode
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100% autocal for life - no adjustments required
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Serial one or two wire interface with auto baud rate
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Fully debounced results
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Patented AKS™ Adjacent Key Suppression
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Spread spectrum bursts for superior noise rejection
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Sync pin for excellent LF noise rejection
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‘Fast mode’ for use in slider type applications
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RoHS compliant 32-QFN, 48-SSOP packages
SNS8
SNS8K
SNS9
SNS9K
N.C.
/CHANGE
1W
RX
25
26
27
28
29
30
31
32
QT1101
10 K
EY
QT
OUCH
™ S
ENSOR
IC
SYNC/LP
DETECT
SNS7K
SNS6K
SNS5K
SNS7
SNS6
VSS
24 23 22 21 20 19 18 17
16
15
14
SNS5
SNS4K
SNS4
SNS3K
SNS3
SNS2K
SNS2
SNS1K
QT1101
32-QFN
13
12
11
10
9
1
SS
2
/RST
3
VDD
4
OSC
5
N.C.
6
SNS0
7
SNS0K
8
SNS1
APPLICATIONS
!
!
MP3 players
Mobile phones
!
!
PC peripherals
Television controls
!
!
Pointing devices
Remote controls
QT1101 charge-transfer (‘QT’) QTouch
TM
IC is a self-contained, patented digital controller capable of detecting near-proximity or touch
on up to ten electrodes. It allows electrodes to project independent sense fields through any dielectric such as glass or plastic. This
capability coupled with its continuous self-calibration feature can lead to entirely new product concepts, adding high value to product
designs. The devices are designed specifically for human interfaces, like control panels, appliances, gaming devices, lighting controls,
or anywhere a mechanical switch or button may be found; they may also be used for some material sensing and control applications.
Each of the channels operates independently of the others, and each can be tuned for a unique sensitivity level by simply changing a
corresponding external Cs capacitor.
Patented AKS™ Adjacent Key Suppression suppresses touch from weaker responding keys and allows only a dominant key to detect,
for example to solve the problem of large fingers on tightly spaced keys.
Spread spectrum burst technology provides superior noise rejection. These devices also have a SYNC/LP pin which allows for
synchronization with additional similar parts and/or to an external source to suppress interference, or, an LP (low power) mode which
conserves power.
By using the charge transfer principle, this device delivers a level of performance clearly superior to older technologies yet is highly
cost-effective.
T
A
-40 C to +85 C
0
0
AVAILABLE OPTIONS
32-QFN
QT1101-ISG
48-SSOP
QT1101-IS48G
LQ
C
Copyright © 2005-2006 QRG Ltd
QT1101 R4.06/0806
1 Overview
The QT1101 is an easy to use, ten touch-key sensor IC
based on Quantum’s patented charge-transfer (‘QT’)
principles for robust operation and ease of design. This
device has many advanced features which provide for
reliable, trouble-free operation over the life of the product.
Burst operation:
The device operates in ‘burst mode’. Each
key is acquired using a burst of charge-transfer sensing
pulses whose count varies depending on the value of the
reference capacitor Cs and the load capacitance Cx. In LP
mode, the device sleeps in an ultra-low current state
between bursts to conserve power. The keys signals are
acquired using three successive bursts of pulses:
Burst A: Keys 0, 1, 4, 5
Burst B: Keys 2, 3, 6, 7
Burst C: Keys 8, 9
Bursts always operate in A-B-C sequence.
Self-calibration:
On power-up, all ten keys are
self-calibrated within 450ms typical to provide reliable
operation under almost any conditions.
Auto-recalibration:
The device can time out and recalibrate
each key independently after a fixed interval of continuous
touch detection, so that the keys can never become ‘stuck
on’ due to foreign objects or other sudden influences. After
recalibration the key will continue to function normally. The
delay is selectable to be either 10s, 60s, or infinite
(disabled).
The device also auto-recalibrates a key when its signal
reflects a sufficient decrease in capacitance. I n this case the
device recalibrates after ~2 seconds so as to recover normal
operation quickly.
Drift compensation
operates to correct the reference level
of each key slowly but automatically over time, to suppress
false detections caused by changes in temperature,
humidity, dirt and other environmental effects.
The drift compensation is asymmetric. In the increasing
capacitive load direction the device drifts more slowly than in
the decreasing direction. In the increasing direction, the rate
of compensation is one count of signal per two seconds. In
the opposing direction, it is one count every 500ms.
Detection Integrator (DI) confirmation
reduces the effects
of noise on the QT1101 outputs. The DI mechanism requires
consecutive detections over a number of measurement
bursts for a touch to be confirmed and indicated on the
outputs. In a like manner, the end of a touch (loss of signal)
has to be confirmed over a number of measurement bursts.
This process acts as a type of ‘ debounce’ against noise.
In normal operation, both the start and end of a touch must
be confirmed for six measurement bursts. In a special ‘Fast
Detect‘ mode (available via jumper resistors) (Tables 1.2 and
1.6), confirmation of the start of a touch requires only two
sequential detections, but confirmation of the end of a touch
is still six bursts.
Fast detect is only available when AKS is disabled.
Spread Spectrum operation:
The bursts operate over a
spread of frequencies, so that external fields will have
minimal effect on key operation and emissions are very
weak. Spread spectrum operation works with the DI
mechanism to dramatically reduce the probability of false
detection due to noise.
Sync Mode:
The QT1101 features a Sync mode to allow the
device to slave to an external signal source, such as a mains
signal (50/60Hz), to limit interference effects. This is
performed using the SYNC/LP pin. Sync mode operates by
triggering three sequential acquire bursts, in sequence
A-B-C from the Sync signal. Thus, each Sync pulse causes
all ten keys to be acquired.
Low Power (LP) Mode:
The device features an LP mode for
microamp levels of current drain with a slower response
time, to allow use in battery operated devices. On detection
of touch, the device automatically reverts to its normal mode
and asserts the DETECT pin active to wake up a host
controller. The device remains in normal, full acquire speed
mode until another pulse is seen on its SYNC/LP pin, upon
which it goes back to LP mode.
AKS™ Adjacent Key Suppression
is a patented feature
that can be enabled via jumper resistors. AKS works to
prevent multiple keys from responding to a single touch, a
common complaint about capacitive touch panels. This can
happen with closely spaced keys, or with control surfaces
that have water films on them.
AKS operates by comparing signal strengths from keys
within a group of keys to suppress touch detections from
those that have a weaker signal change than the dominant
one.
The QT1101 has two different AKS groupings of keys,
selectable via option resistors. These groupings are:
AKS operates in three groups of keys.
AKS operates over all ten keys.
These two modes allow the designer to provide AKS while
also providing for shift or function operations.
If AKS is disabled, all keys can operate simultaneously.
Outputs:
The QT1101 has a serial output using one or two
wires, RS-232 data format, and automatic baud rate
detection. A simple protocol is employed.
The QT1101 operates in slave mode, i.e. it only sends data
to the host after receiving a request from the host.
An additional /CHANGE (state changed) signal allows the
use of the serial interface to be optimised, rather than being
polled continuously.
Simplified Mode:
To reduce the need for option resistors,
the simplified operating mode places the part into fixed
settings with only the AKS feature being selectable. LP
mode is also possible in this configuration. Simplified mode
is suitable for most applications.
Lq
2
QT1101 R4.06/0806
NXP MCU
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