lQ
This datasheet is applicable to all revision 1 chips
SYNC/LP
VSS
DETECT
SNS7K
SNS7
QT1081
8-K
EY
QT
OUCH
™ S
ENSOR
IC
The QT1081 is an improved, lower cost, simplified circuit version of the
popular QT1080 sensor IC. The QT1081 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.
The QT1081 is also compatible with clear films to make simple
button-style touch screens over LCD displays.
OUT_0 25
OUT_1 26
OUT_2 27
OUT_3 28
OUT_4 29
OUT_5 30
OUT_6 31
OUT_7 32
24 23 22 21 20 19 18 17
16 SNS5
15 SNS4K
14 SNS4
13 SNS3K
12 SNS3
11 SNS2K
10 SNS2
6
SNS0
7
SNS0K
9
8
SNS1
SN1K
QT1081
32-QFN
1
SS
2 3 4 5
/RST
VDD
OSC
N/C
AT A GLANCE
Number of keys:
Technology:
Key outline sizes:
Key spacings:
Electrode design:
Layers required:
Substrates:
Electrode materials:
Panel materials:
Adjacent Metal:
Panel thickness:
Key sensitivity:
Outputs:
Moisture tolerance:
Power:
Package:
Signal processing:
Applications:
Patents:
1 to 8
Patented spread-spectrum charge-transfer (one-per-key mode)
5mm x 5mm or larger (panel thickness dependent); widely different sizes and shapes possible
6mm or wider, center to center (panel thickness, human factors dependent)
Single solid or ring shaped electrodes; wide variety of possible layouts
One layer substrate; electrodes and components can be on same side
FR-4, low cost CEM-1 or FR-2 PCB materials; polyamide FPCB; PET films, glass
Copper, silver, carbon, ITO, Orgacon
†
ink (virtually anything electrically conductive)
Plastic, glass, composites, painted surfaces (low particle density metallic paints possible)
Compatible with grounded metal immediately next to keys
Up to 50mm glass, 20mm plastic (key size dependent)
Settable via change in reference capacitor (Cs) value
Parallel discrete output, one-per-key, active-high
Good
2.8V ~ 5.0V, <15µA (8 keys at 2.8V, 340ms Low Power mode).
32-pin 5 x 5mm QFN RoHS compliant
Self-calibration, auto drift compensation, noise filtering, patented Adjacent Key Suppression
TM
Portable devices, domestic appliances and A/V gear, PC peripherals, office equipment
AKS™
(patented Adjacent Key Suppression)
QTouch™
(patented Charge-transfer method)
†
Orgacon is a registered trademark of Agfa-Gevaert N.V
AVAILABLE OPTION
T
A
32-QFN
-40
o
C to +85
o
C
QT1081-ISG
LQ
Copyright © 2006-2007 QRG Ltd
QT1081_1R0.04_0307
SNS6K
SNS6
SNS5K
Contents
1 Overview
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3
1.1 Differences With QT1080
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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™)
. . . . . . . . . . . . . . . . . . . . . .
3
1.2.11 Outputs
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
1.2.12 Simplified Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4
1.3 Wiring
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5
2 Device Operation
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.1 Start-up Time
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.2 Option Resistors
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.3 One-per-key Output Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.4 Binary Coded Output Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.5 DETECT Pin
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.6 SYNC/LP Pin
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
2.7 AKS™ Function Pins
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
2.8 MOD_0, MOD_1 Inputs
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
2.9 Fast Detect Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
9
2.10 Simplified Mode
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
2.11 Unused Keys
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10
3 Design Notes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
3.1 Oscillator Frequency
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
3.2 Spread-Spectrum Circuit
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
3.3 Cs Sample Capacitors - Sensitivity
. . . . . . . . . . . . . . . . . . . . . .
11
3.4 Power Supply
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
11
3.5 PCB Layout and Construction
. . . . . . . . . . . . . . . . . . . . . . . . . .
11
4 Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
4.1 Absolute Maximum Specifications
. . . . . . . . . . . . . . . . . . . . . . .
12
4.2 Recommended Operating Conditions
. . . . . . . . . . . . . . . . . . . .
12
4.3 AC Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
4.4 DC Specifications
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12
4.5 Signal Processing
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
4.6 Average Idd Curves
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14
4.7 LP Mode Typical Response Times
. . . . . . . . . . . . . . . . . . . . . .
15
4.8 Mechanical - 32-QFN Package
. . . . . . . . . . . . . . . . . . . . . . . . .
16
4.9 Part Marking
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17
4.10 Moisture Sensitivity Level (MSL)
. . . . . . . . . . . . . . . . . . . . . . .
17
5 Datasheet Control
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
5.1 Changes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
5.2 Numbering Convention
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18
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2
QT1081_1R0.04_0307
1 Overview
1.1
Differences With QT1080
The QT1081 is a general replacement device for the highly
popular QT1080. 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 B’ only mode for lower key counts with less power
The QT1081 should be used over the QT1080 for new
designs due to a simpler circuit, lower power and lower cost.
1.2.6 Detection Integrator Confirmation
Detection Integrator (DI) confirmation reduces the effects of
noise on the QT1081. The ‘detect integrator’ 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, 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), 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.
1.2 Parameters
1.2.1 Introduction
The QT1081 is an easy to use, eight-touch-key sensor IC
based on Quantum’s patented charge-transfer 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 two successive bursts of
pulses:
Burst A: Keys 0, 1, 4, 5
Burst B: Keys 2, 3, 6, 7
Bursts always operate in A-B sequence.
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 QT1081 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 two
sequential acquire bursts, in sequence A-B from the Sync
signal. Thus, each Sync pulse causes all eight keys to be
acquired.
1.2.3 Self-calibration
On power-up, all eight keys are self- calibrated within 300
milliseconds (typical) to provide reliable operation under
almost any conditions.
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 touch detection, 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 requested to
return to LP mode.
When four or fewer keys are required, current drain in LP
mode can be further reduced by choosing appropriate
channels on the QT1081.
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.
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 2 seconds; in the
opposing direction, it is one count every 500ms.
1.2.10 Adjacent Key Suppression (AKS™)
AKS™
is a Quantum-patented feature that can be enabled via
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.
lQ
3
QT1081_1R0.04_0307
The QT1081 has two different AKS groupings of keys,
selectable via option resistors. These groupings are:
AKS operates in two groups of four keys.
AKS operates over all eight 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
There are two output modes: one-per-key, and binary coded.
One-per-key output: In this mode there is one output pin per
key. This mode has two output drive options, push-pull and
open-drain. The outputs can also be made either active-high
or active-low. These options are set via external configuration
resistors.
Binary coded output: In this mode, three output lines encode
for one possible key in detect. If more than one key is
detecting, only the first one touched will be indicated.
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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4
QT1081_1R0.04_0307
1.3 Wiring
Table 1.1 Pinlist
32-QFN
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
Name
SS
/RST
Vdd
OSC
n/c
SNS0
SNS0K
SNS1
SNS1K
SNS2
SNS2K
SNS3
SNS3K
SNS4
SNS4K
SNS5
SNS5K
SNS6
SNS6K
SNS7
SN7K
Vss
SYNC/LP
‡
DETECT
OUT_0
OUT_1
OUT_2
OUT_3
OUT_4
OUT_5
OUT_6
OUT_7
Type
OD
I
Pwr
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
Pwr
I
O/OD
O/OD
O/OD
O/OD
O/OD
O/OD
O/OD
O/OD
O/OD
Function
Spread spectrum
Reset input
Power
Notes
If Unused
100K resistor to Vss
Vdd
-
-
-
Option resistor
Open
Open or
option resistor*
Open
Open or
option resistor*
Open
Open or
option resistor*
Open
Open or
option resistor*
Open
Open or
option resistor*
Open
Open or
option resistor*
Open or
mode resistor
†
Open or mode resistor
†
or option resistor*
Open
-
Vdd or Vss
Open
Open
Open
Open
Open
Open
Open
Open
Open
Spread spectrum drive
Active low reset
+2.8 ~ +5.0V
Resistor to Vdd and optional
Oscillator
spread spectrum RC network
-
Leave open
Sense pin and
To Cs0 and/or
option select
option resistor
Sense pin
To Cs0 + Key
Sense pin and
To Cs1 and/or
option select
option resistor*
Sense pin
To Cs1 + Key
Sense pin and
To Cs2 and/or
option select
option resistor*
Sense pin
To Cs2 + Key
Sense pin and
To Cs3 and/or
option select
option resistor*
Sense pin
To Cs3 + Key
Sense pin and
To Cs4 and/or
option select
option resistor*
Sense pin
To Cs4 + Key
Sense pin and
To Cs5 and/or
option select
option resistor*
Sense pin
To Cs5 + Key
Sense pin and
To Cs6 and/or
option select
option resistor*
Sense pin and
To Cs6 + Key and/or
mode select
mode resistor
†
Sense pin and mode To Cs7 and/or mode resistor
†
or option select
or option resistor*
Sense pin
To Cs7 + Key
Ground
0V
Sync In or LP In
Rising edge sync or LP pulse
Detect Status
Active = any key in detect
Out 0
Also, binary coded output 0
Out 1
Also, binary coded output 1
Out 2
Also, binary coded output 2
Out 3
Out 4
In binary coded mode, these pins
Out 5
are clamped internally to Vss
Out 6
Out 7
Pin Type
I
I/O
O
OD
O/OD
Pwr
CMOS input only
CMOS I/O
CMOS push-pull output
CMOS open drain output
CMOS push pull or open-drain output (option selected)
Power / ground
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)
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5
QT1081_1R0.04_0307
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