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PDF QT1081 Data sheet ( Hoja de datos )
| Número de pieza | QT1081 | |
| Descripción | 8-KEY QTOUCH SENSOR IC | |
| Fabricantes | Quantum | |
| Logotipo |  |
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lQ
This datasheet is applicable to all revision 1 chips
QT1081
8-KEY QTOUCH™ SENSOR 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.
24 23 22 21 20 19 18 17
OUT_0 25
16 SNS5
OUT_1 26
15 SNS4K
OUT_2 27
14 SNS4
OUT_3 28
OUT_4 29
QT1081
32-QFN
13 SNS3K
12 SNS3
OUT_5 30
11 SNS2K
OUT_6 31
10 SNS2
OUT_7 32
9 SN1K
1 2345 6 7 8
AT A GLANCE
Number of keys:
Technology:
Keywww.DataSheet4U.com 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 SuppressionTM
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
LQ
AVAILABLE OPTION
TA
-40oC to +85oC
32-QFN
QT1081-ISG
Copyright © 2006-2007 QRG Ltd
QT1081_1R0.04_0307
1 page  
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
Notes
If Unused
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 and
option select
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
Out 0
Out 1
Out 2
Out 3
Out 4
Out 5
Out 6
Out 7
Spread spectrum drive
100K resistor to Vss
Active low reset
Vdd
+2.8 ~ +5.0V
-
Resistor to Vdd and optional
spread spectrum RC network
Leave open
-
-
To Cs0 and/or
option resistor
To Cs0 + Key
Option resistor
Open
To Cs1 and/or
option resistor*
Open or
option resistor*
To Cs1 + Key
Open
To Cs2 and/or
option resistor*
To Cs2 + Key
Open or
option resistor*
Open
To Cs3 and/or
option resistor*
To Cs3 + Key
Open or
option resistor*
Open
To Cs4 and/or
option resistor*
Open or
option resistor*
To Cs4 + Key
Open
To Cs5 and/or
option resistor*
Open or
option resistor*
To Cs5 + Key
Open
To Cs6 and/or
option resistor*
Open or
option resistor*
To Cs6 + Key and/or
mode resistor†
To Cs7 and/or mode resistor†
or option resistor*
Open or
mode resistor†
Open or mode resistor†
or option resistor*
To Cs7 + Key
Open
0V -
Rising edge sync or LP pulse Vdd or Vss
Active = any key in detect
Open
Also, binary coded output 0
Open
Also, binary coded output 1
Open
Also, binary coded output 2
Open
Open
Open
In binary coded mode,
are clamped internally
these pins
to Vss
Open
Open
Open
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)
lQ
5
QT1081_1R0.04_0307
5 Page 
3 Design Notes
3.1 Oscillator Frequency
The QT1081’s internal oscillator runs from an external resistor
network connected to the OSC and SS pins, as shown in
Figures 1.1 and 1.2, to achieve spread-spectrum operation. If
spread-spectrum mode is not required, the OSC pin should be
connected to Vdd with an 18KΩ one percent resistor.
Under different Vdd voltage conditions the resistor network (or
the solitary 18KΩ resistor) might require minor adjustment to
obtain the specified burst center frequency. The network
should be adjusted slightly so that the positive pulses on any
key are approximately 2.67µs wide in the ‘solitary 18KΩ
resistor’ mode, or 2.87µs wide at the beginning of a burst with
the recommended spread-spectrum circuit (see next section).
In practice, the pulse width has little effect on circuit
performance if it varies in the range of 2µs to 3.3µs. The only
effects seen will be proportional variations in Max On-Duration
and non-LP mode response times.
3.2 Spread-Spectrum Circuit
The QT1081 offers the ability to spectrally spread its
frequency of operation to heavily reduce susceptibility to
external noise sources and to limit RF emissions. The SS pin
is used to modulate an external passive RC network that
modulates the OSC pin. OSC is the main oscillator current
input. The circuit is shown in both Figures 1.1 and 1.2.
The resistors Rb1 and Rb2 should be changed depending on
Vdd. As shown in Figures 1.1 and 1.2, two sets of values are
recommended for these resistors depending on Vdd. The
power curves in Section 4.6 also show the effect of these
resistors.
The circuit can be eliminated, if it is not desired, by using an
18KΩ resistor from OSC to Vdd to drive the oscillator, and
connecting SS to Vss with a 100KΩ resistor.
The spread-spectrum RC network will need to be adjusted
according to the burst lengths. The sawtooth waveform
observed on SS should reach a crest height as follows:
Vdd >= 3.6V: 17 percent of Vdd
Vdd < 3.6V: 20 percent of Vdd
The Css capacitor connected to the SS pin (Figures 1.1 and
1.2) should be adjusted so that the waveform approximates
the above amplitude, ±10 percent, during normal operation in
the target circuit. Where the bursts are of differing lengths, the
adjustment should be done for the longer burst. If this is done,
the circuit will give a spectral modulation of 12-15 percent.
Use of the spread-spectrum facility has the following effect on
Idd:
• Full speed operation: Idd changes within ±10 percent.
• Idd increases by up to 15 percent.
In both cases the exact value depends on the precise circuit
component values and timing. Vdd variations can shift the
center frequency and spread slightly.
3.3 Cs Sample Capacitors - Sensitivity
The Cs sample capacitors accumulate the charge from the
key electrodes and determine sensitivity. Higher values of Cs
make the corresponding sensing channel more sensitive. The
values of Cs can differ for each channel, permitting
differences in sensitivity from key to key or to balance unequal
sensitivities. Unequal sensitivities can occur due to key size
and placement differences and stray wiring capacitances.
More stray capacitance on a sense trace will desensitize the
corresponding key; increasing the Cs for that key will
compensate for the loss of sensitivity.
The Cs capacitors can be virtually any plastic film or low to
medium-K ceramic capacitor. The normal Cs range is 1nF to
50nF depending on the sensitivity required; larger values of
Cs require better quality to ensure reliable sensing. In certain
circumstances the normal Cs range may be exceeded, hence
the different values in Section 4.2. Acceptable capacitor types
for most uses include PPS film, polypropylene film, and NP0
and X5R / X7R ceramics. Lower grades than X5R or X7R are
not recommended.
The required values of Cs can be noticeably affected by the
presence and connection of the option resistors (see
Section 2.2). Cs values should be adjusted for optimal
sensitivity after the option resistors are connected.
3.4 Power Supply
The power supply can range from 2.8 to 5.0 volts. If this
fluctuates slowly with temperature, the device will track and
compensate for these changes automatically with only minor
changes in sensitivity. If the supply voltage drifts or shifts
quickly, the drift compensation mechanism will not be able to
keep up, causing sensitivity anomalies or false detections.
The power supply should be locally regulated, using a
three-terminal device, to between 2.8V and 5.0V. If the supply
is shared with another electronic system, care should be taken
to ensure that the supply is free of digital spikes, sags and
surges which can cause adverse effects. It is not
recommended to include a series inductor in the power supply
to the QT1081.
For proper operation a 0.1µF or greater bypass capacitor
must be used between Vdd and Vss; the bypass capacitor
should be routed with very short tracks to the device’s Vss
and Vdd pins.
3.5 PCB Layout and Construction
Refer to Quantum application note AN-KD02 for information
related to layout and construction matters.
lQ
11
QT1081_1R0.04_0307
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet QT1081.PDF ] | |
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