Quantum QT1081 Technical data

lQ

QT1081

This datasheet is applicable to all revision 1 chips

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.

8-KEY QT

DETECT

23

OUT_0
OUT_1
OUT_2
OUT_3
OUT_4
OUT_5
OUT_6

25
26
27
28
29
30
31
32OUT_7

24

1

SS

OUCH

SYNC/LP

VSS21SNS7K

22

QT1081
32-QFN

2

3

VDD

/RST

4

OSC

™ S

SNS7

20

19

5

N/C

SNS6K18SNS6

6

SNS0

SNS5K

17

16
15

14
13
12

11
10

9

7

8

SNS1

SNS0K

ENSOR

SNS5
SNS4K

SNS4

SNS3K
SNS3
SNS2K

SNS2
SN1K

IC

AT A GLANCE

Number of keys: 1 to 8
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: FR-4, low cost CEM-1 or FR-2 PCB materials; polyamide FPCB; PET films, glass
Electrode materials: Copper, silver, carbon, ITO, Orgacon
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: Parallel discrete output, one-per-key, active-high
Moisture tolerance: Good
Power: 2.8V ~ 5.0V, <15µA (8 keys at 2.8V, 340ms Low Power mode).
Package: 32-pin 5 x 5mm QFN RoHS compliant
Signal processing: Self-calibration, auto drift compensation, noise filtering, patented Adjacent Key Suppression
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

†

ink (virtually anything electrically conductive)

TM

LQ

AVAILABLE OPTION

A

o

C to +85oC

32-QFNT

QT1081-ISG-40

Copyright © 2006-2007 QRG Ltd

QT1081_1R0.04_0307

Contents

1 Overview

1.1 Differences With QT1080

1.2 Parameters

1.3 Wiring

2 Device Operation

2.1 Start-up Time

2.2 Option Resistors

2.3 One-per-key Output Mode

2.4 Binary Coded Output Mode

2.5 DETECT Pin

2.6 SYNC/LP Pin

2.7 AKS™ Function Pins

2.8 MOD_0, MOD_1 Inputs

...........................................

1.2.1 Introduction

1.2.2 Burst Operation

1.2.3 Self-calibration

1.2.4 Autorecalibration

1.2.5 Drift Compensation

1.2.6 Detection Integrator Confirmation

1.2.7 Spread-spectrum Operation

1.2.8 Sync Mode

1.2.9 Low Power (LP) Mode

1.2.10 Adjacent Key Suppression (AKS™)

1.2.11 Outputs

1.2.12 Simplified Mode

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2.9 Fast Detect Mode

3

2.10 Simplified Mode

3

2.11 Unused Keys

3

3 Design Notes

3

3.1 Oscillator Frequency

3

3.2 Spread-Spectrum Circuit

3

3.3 Cs Sample Capacitors - Sensitivity

3

3.4 Power Supply

3

3.5 PCB Layout and Construction

3

4 Specifications

3

4.1 Absolute Maximum Specifications

3

4.2 Recommended Operating Conditions

3

4.3 AC Specifications

3

4.4 DC Specifications

4

4.5 Signal Processing

4

4.6 Average Idd Curves

5

4.7 LP Mode Typical Response Times

8

4.8 Mechanical - 32-QFN Package

8

4.9 Part Marking

8

4.10 Moisture Sensitivity Level (MSL)

8

5 Datasheet Control

8

5.1 Changes

8

5.2 Numbering Convention

8
9
9

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lQ

2 QT1081_1R0.04_0307

1 Overvie

w

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 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.

1.2.3 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.

1.2.5 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.

1.2.6 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.

1.2.7 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.

1.2.9 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.

1.2.10 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:

y AKS operates in two groups of four keys.
y 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.

-per-key output: In this mode there is one output pin per

One
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:
for one possible key in detect. If more than one key is
detecting, only the first one touched will be indicated.

In this mode, three output lines encode

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.

lQ 4 QT1081_1R0.04_0307

1.3 Wiring

32-QFN

Table 1.1 Pinlist

Pin

OscillatorIOSC4

Sense pin and

option select

Sense pin and

option select

Sense pin and

option select

Sense pin and

option select

Sense pin and

option select

Sense pin and

option select

Sense pin and

option select

Sense pin and

mode select

Sense pin and mode

or option select

23

SNS06

I/O

I/OSNS18

I/OSNS210

I/OSNS312

I/OSNS414

I/OSNS516

I/OSNS618
I/OSNS6K19
I/OSNS720

‡

Out 2O/ODOUT_227
Out 3O/ODOUT_328

Pin Type

I CMOS input only
I/O CMOS I/O
O CMOS push-pull output
OD CMOS open drain output
O/OD CMOS push pull or open-drain output (option selected)
Pwr 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)

Resistor to Vdd and optional
spread spectrum RC network

To Cs0 and/or
option resistor

To Cs1 and/or
option resistor*

To Cs2 and/or
option resistor*

To Cs3 and/or
option resistor*

To Cs4 and/or
option resistor*

To Cs5 and/or
option resistor*

To Cs6 and/or
option resistor*
To Cs6 + Key and/or
mode resistor
To Cs7 and/or mode resistor

†

†

or option resistor*

Also, binary coded output 2

In binary coded mode, these pins
are clamped internally to Vss

If UnusedNotesFunctionTypeName

100K resistor to VssSpread spectrum driveSpread spectrumODSS1
VddActive low resetReset inputI/RST2

-+2.8 ~ +5.0VPowerPwrVdd3

-

-Leave open--n/c5
Option resistor
OpenTo Cs0 + KeySense pinI/OSNS0K7

Open or
option resistor*
OpenTo Cs1 + KeySense pinI/OSNS1K9
Open or
option resistor*
OpenTo Cs2 + KeySense pinI/OSNS2K11
Open or
option resistor*
OpenTo Cs3 + KeySense pinI/OSNS3K13
Open or
option resistor*
OpenTo Cs4 + KeySense pinI/OSNS4K15
Open or
option resistor*
OpenTo Cs5 + KeySense pinI/OSNS5K17
Open or
option resistor*
Open or
mode resistor
Open or mode resistor
or option resistor*
OpenTo Cs7 + KeySense pinI/OSN7K21

-0VGroundPwrVss22
Vdd or VssRising edge sync or LP pulseSync In or LP InISYNC/LP
OpenActive = any key in detectDetect StatusO/ODDETECT24
OpenAlso, binary coded output 0Out 0O/ODOUT_025
OpenAlso, binary coded output 1Out 1O/ODOUT_126
Open
Open
OpenOut 4O/ODOUT_429

OpenOut 5O/ODOUT_530
OpenOut 6O/ODOUT_631
OpenOut 7O/ODOUT_732

†

†

lQ 5 QT1081_1R0.04_0307

Figure 1.1 Connection Diagram - Full Options

KEY 3

KEY 4

KEY 5

KEY 6

KEY 7

SYNC or LP IN

DETECT OUT

Vunreg

*4.7uF *4.7uF *100nF

+2.8 ~ +5V

Voltage Reg

Keep these parts

close to the IC

MOD_1
Vdd / Vss

R

SNS3

10K

POL
Vdd / Vss

R

SNS4

10K

OUT_D

Vdd / Vss

R

SNS5

10K

SL_0
Vdd / Vss

R

SNS6

10K

SL_1
Vdd / Vss

R

SNS7

10K

1M

1nF

1M

1nF

1M

1nF

1M

1nF

1M

1nF

VDD

2

12

SNS3

C

S3

13

SNS3K

14

SNS4

C

S4

15

SNS4K

16

SNS5

SNS5K

18

SNS6

19

SNS6K

20

SNS7

C

S7

21

SNS7K

22

VSS

23

SYNC/LP

24

DETECT

3

VDD

/RST

QT1081
32-QFN

* Note: one bypass capacitor to be tightly wired

between Vdd and Vss. Follow manufacturer’s
recommendations for input and output capacitors.

Keep these parts

close to the IC

1nF

11

SNS2K

SNS2

SNS1K

SNS1

SNS0K

SNS0

OSC

SS
OUT_7
OUT_6
OUT_5
OUT_4
OUT_3
OUT_2
OUT_1
OUT_0

10

9

8

7

6

4

1
32
31
30
29
28
27
26
25

C

1nF

C

1nF

C

VDD

Rb1

Rb2

10K

S2

R

SNS2

1M

MOD_0

Vdd / Vss

S1

S0

10K

R

SNS1

1M

AKS_1

Vdd / Vss

10K

SNS0

R

1M

AKS_0

Vdd / Vss

The required value of spread-spectrum capacitor CSS
will vary according to the lengths of the acquire bursts,
see Section 3.2. A typical value of is 100nF.CSS

C

SS

KEY 2

KEY 1

KEY 0

Recommended Rb1, Rb2 Values

OUT_7
OUT_6
OUT_5
OUT_4
OUT_3
OUT_2
OUT_1
OUT_0

OUT_0

Rb1 Rb2

15K 27K

Binary coded
output mode

Vdd Range

2.8 ~ 3.59V 12K 22K

3.6 ~ 5V

Table 1.2

AKS / Fast-Detect Options

Table 1.3

Max On-Duration

Table 1.4

Polarity and Output

Table 1.5

SYNC/LP Function

FAST-DETECTAKS MODEAKS_0AKS_1

OffOffVssVss
EnabledOffVddVss
OffOn, in 2 groupsVssVdd
OffOn, globalVddVdd

MAX ON-DURATION MODEMOD_0MOD_1

10 seconds (nom) to recalibrateVssVss
60 seconds (nom) to recalibrateVddVss
Infinite (disabled)VssVdd
(reserved)VddVdd

OUT_n, DETECT PIN MODEPOLOUT_D

Binary coded, active high, push-pullVssVss
One-per-key, active low, open-drainVddVss
One-per-key, active high, push-pullVssVdd
One-per-key, active low, push-pullVddVdd

SYNC/LP PIN MODESL_0SL_1

SyncVssVss
LP mode: 100ms nom response timeVddVss
LP mode: 180ms nom response timeVssVdd
LP mode: 340ms nom response timeVddVdd

lQ 6 QT1081_1R0.04_0307