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QT1103
QTOUCH™ 10-KEY SENSOR IC
This datasheet is applicable to all revision 3 chips
The QT1103 is designed for low cost appliance, mobile, and consumer
electronics applications.
QTouch™ technology is a type of patented charge-transfer sensing
method well known for its robust, stable, EMC-resistant characteristics.
It is the only all-digital capacitive sensing technology in the market
today. This technology has over a decade of applications experience
spanning thousands of designs.
QTouch circuits are renowned for simplicity, reliability, ease of design,
and cost effectiveness.
QTouch™ sensors employ a single reference capacitor tied to two pins
of the chip for each sensing key; a signal trace leads from one of the
pins to the sensing electrode which forms the key. The sensing
electrode can be a simple solid shape such as a rectangle or circle. An
LED can be placed near or inside the solid circle for illumination.
The key electrodes can be designed into a conventional Printed Circuit
Board (PCB) or Flexible Printed Circuit Board (FPCB) as a copper
pattern, or as printed conductive ink on plastic film.
24 23 22 21 20 19 18 17
SNS8
SNS8K
SNS9
SNS9K
N/C
/CHANGE
1W
RX
25
26
27
28
29
30
31
32
QT1103
1 234 56 78
16 SNS5
15 SNS4K
14 SNS4
13 SNS3K
12 SNS3
11 SNS2K
10 SNS2
9 SNS1K
AT A GLANCE
Number of keys:
1 to 10
Technology:
Patented spread-spectrum charge-transfer (one-per-key mode)
Key outline sizes:
5mm x 5mm or larger (panel thickness dependent); widely different sizes and shapes possible
Key spacings:
6mm or wider, center to center (panel thickness, human factors dependent)
Electrode design:
Single solid or ring shaped electrodes; wide variety of possible layouts
Layers required:
One layer substrate; electrodes and components can be on same side
Substrates:
Electrode materials:
FR-4, low cost CEM-1 or FR-2 PCB materials; polyamide FPCB; PET films, glass
Copper, silver, carbon, ITO, Orgaconink (virtually anything electrically conductive)
Panel materials:
Plastic, glass, composites, painted surfaces (low particle density metallic paints possible)
Adjacent Metal:
Compatible with grounded metal immediately next to keys
Panel thickness:
Up to 50mm glass, 20mm plastic (key size dependent)
Key sensitivity:
Settable via change in reference capacitor (Cs) value
Outputs:
RS-232 based serial output, capable of single-wire operation
Moisture tolerance:
Good
Power:
2.8V ~ 5.0V
Package:
32-pin 5 x 5mm QFN RoHS compliant
Signal processing:
Self-calibration, auto drift compensation, noise filtering, AKS
Applications:
Portable devices, domestic appliances and A/V gear, PC peripherals, office equipment
Patents:
AKS™ (patented Adjacent Key Suppression)
QTouch™ (patented Charge-transfer method)
Orgacon is a registered trademark of Agfa-Gevaert N.V
AVAILABLE OPTIONS
TA
-400C to +850C
32-QFN
QT1103-ISG
LQ
CCopyright © 2006-2007 QRG Ltd
QT1103_3R0.03_0607

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Contents
1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Differences With QT1101 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.2 Burst Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.3 Self-calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.4 Autorecalibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.5 Drift Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.6 Detection Integrator Confirmation . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.7 Spread-spectrum Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.8 Sync Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.9 Low Power (LP) Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2.10 Adjacent Key Suppression (AKS™) . . . . . . . . . . . . . . . . . . . . . . 4
1.2.11 Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2.12 Simplified Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3 Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Device Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Reset and Startup Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Option Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 DETECT Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.4 /CHANGE Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5 SYNC/LP Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5.2 Sync Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.5.3 Low Power (LP) Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.6 AKS™ Function Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.7 MOD_0, MOD_1 Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.8 Fast Detect Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.9 Simplified Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.10 Unused Keys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.11 Serial 1W Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.11.2 Basic 1W Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.11.3 LP Mode Effects on 1W . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.11.4 2W Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Design Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.1 Oscillator Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.2 Spread-spectrum Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3 Cs Sample Capacitors - Sensitivity . . . . . . . . . . . . . . . . . . . . . . 12
3.4 Rsns Resistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.5 Power Supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.6 PCB Layout and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1 Absolute Maximum Specifications . . . . . . . . . . . . . . . . . . . . . . . 13
4.2 Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . 13
4.3 AC Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.4 DC Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.5 Signal Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.6 Idd Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
4.7 LP Mode Typical Response Times . . . . . . . . . . . . . . . . . . . . . . 18
4.8 Mechanical Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.9 Part Marking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.10 Moisture Sensitivity Level (MSL) . . . . . . . . . . . . . . . . . . . . . . . 20
5 Datasheet Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1 Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2 Numbering Convention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
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1 Overview
1.1 Differences With QT1101
The QT1103 is a general replacement device for the highly
popular QT1101. It has all of the same features as the older
device but differs in the following ways:
Rs resistors on each channel eliminated
Up to 4x more sensitive for a given value of Cs
Shorter burst lengths, less power for a given value of
Cs
‘Burst A and B’ only mode for up to eight keys, with
less power
‘Burst B’ only mode for up to four keys, with less
power than ‘Burst A and B’ mode
Requires an external reset signal
The QT1103 should be used instead of the QT1101 for new
designs due to a simpler circuit, lower power and lower cost.
1.2 Parameters
1.2.1 Introduction
The QT1103 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.
1.2.2 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 C-A-B sequence.
1.2.3 Self-calibration
On power-up, all ten keys are self-calibrated within 300ms
(typical) to provide reliable operation under almost any
conditions.
1.2.5 Drift Compensation
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.
1.2.6 Detection Integrator Confirmation
Detection Integrator (DI) confirmation reduces the effects of
noise on the QT1103. 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.
A per-key counter is incremented each time the key has
exceeded its threshold and stayed there for a number of
measurement bursts. When this counter reaches a preset
limit the key is finally declared to be touched.
For example, if the limit value is six, then the device has to
exceed its threshold and stay there for six measurement
bursts in succession without going below the threshold level,
before the key is declared to be touched. If on any
measurement burst the signal is not seen to exceed the
threshold level, the counter is cleared and the process has to
start from the beginning.
In normal operation, the start of a touch must be confirmed
for six measurement bursts and the end of a touch for three.
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 three and the end of a touch requires two
measurement bursts.
Fast detect is only available when AKS is disabled.
1.2.7 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.
1.2.8 Sync Mode
The QT1103 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 C-A-B from the
Sync signal. Thus, each Sync pulse causes all ten keys to be
acquired (see Section 2.5.2, page 8).
1.2.4 Autorecalibration
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 autorecalibrates a key when its signal
reflects a sufficient decrease in capacitance. In this case the
device recalibrates after ~2 seconds so as to recover normal
operation quickly.
1.2.9 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 (see Optimization of LP Mode, page 9).
When eight or fewer keys are required, current drain in LP
mode can be further reduced by choosing appropriate
channels on the QT1103 (see the end of Section 2.5.3,
page 8).
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1.2.10 Adjacent Key Suppression (AKS™)
AKSis a Quantum-patented feature that can be enabled
via a resistor strap option. 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 QT1103 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.
1.2.11 Outputs
The QT1103 has a serial output using one or two wires,
RS-232 data format, and automatic baud rate detection. A
simple protocol is employed.
The QT1103 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.
1.2.12 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.
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1.3 Wiring
Pin Name
1 SS
2 /RST
3 Vdd
4 OSC
5 n/c
6 SNS0
7 SNS0K
8 SNS1
9 SNS1K
10 SNS2
11 SNS2K
12 SNS3
13 SNS3K
14 SNS4
15 SNS4K
16 SNS5
17 SNS5K
18 SNS6
19 SNS6K
20 SNS7
21 SNS7K
22 Vss
23 SYNC/LP
24 DETECT
25 SNS8
26 SNS8K
27 SNS9
28 SNS9K
29 n/c
30 /CHANGE
31 1W
32 RX
Type
OD
I
P
I
-
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
P
I
O/OD
I/O
I/O
I/O
I/O
-
OD
I/OD
I
Table 1.1 Pin Descriptions
Function
Spread spectrum
Reset input
Power
Oscillator
-
Sense pin and
option select
Sense pin
Sense pin and
option select
Sense pin
Sense pin and
option select
Sense pin
Sense pin and
option select
Sense pin
Sense pin
Sense pin
Sense pin and
option select
Sense pin
Sense pin and
option select
Sense pin and
mode select
Sense pin and mode
or option select
Sense pin
Ground
Sync In or LP In
Detect Status
Sense pin
Sense pin
Sense pin
Sense pin
-
State changed
1W mode serial I/O
2W Receive
Notes
Spread spectrum drive
Active low reset
+2.8 ~ +5.0V
Resistor to Vdd and optional
spread spectrum RC network
Leave open
To Cs0 and/or
option resistor
To Cs0 + Key
To Cs1 and/or
option resistor*
To Cs1 + Key
To Cs2 and/or
option resistor*
To Cs2 + Key
To Cs3 and/or
option resistor*
To Cs3 + Key
To Cs4
To Cs4 + Key
To Cs5 and/or
option resistor *
To Cs5 + Key
To Cs6 and/or
option resistor*
To Cs6 + Key and/or
mode resistor
To Cs7 and/or mode resistor
or option resistor*
To Cs7 + Key
0V
Rising edge sync or LP pulse
See Table 1.4
To Cs8
To Cs8 + Key
To Cs9
To Cs9 + Key
-
0 = a key state has changed
Requires pull-up
Requires pull-up to Vdd
Input for 2W mode
If Unused
100k resistor to Vss
-
-
-
-
Open or
option resistor*
Open
Open or
option resistor*
Open
Open or
option resistor*
Open
Open or
option resistor*
Open
Open
Open
Open or
option resistor*
Open
Open or
option resistor*
Open or
mode resistor
Open or mode resistoror option
resistor*
Open
-
Vdd or Vss**
Open
Open
Open
Open
Open
Open
100k resistor to Vss
-
Vdd
Pin Type
I
I/O
OD
I/OD
O/OD
P
CMOS input only
CMOS I/O
CMOS open drain output
CMOS input or open drain output
CMOS push-pull or open-drain output (option selected)
Ground or power
Notes
Mode resistor is required only in Simplified mode (see Figure 1.2)
* Option resistor is required only in Full Options mode (see Figure 1.1)
Pin is either Sync or LP depending on options selected (functions SL_0, SL_1, see Figure 1.1)
** See text
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