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PDF QT411-ISSG Data sheet ( Hoja de datos )
| Número de pieza | QT411-ISSG | |
| Descripción | Touch Slider IC | |
| Fabricantes | Quantum Research | |
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om QT411-ISSGlQ
et4U.c QS ™ T S ICz QT401 QSlide™ enhancement - simplified calibration
ez Linear finger-touch capacitive slider control
Shz Robust Charge-Transfer sensing method
taz Extremely simple circuit - no external active components
.Daz SPI slave-mode interface
z Self-calibration and drift compensation
wwz Spread-spectrum operation for optimal EMC compliance
wz 2.5 - 5.5V single supply operation; very low power
LIDE
OUCH LIDER
VDD
SDO
/SS
SCLK
SNS3B
1 14
2 13
3 QT411 12
4 11
5 10
GND
DRDY
DETECT
SDI
SNS1A
z Enhanced power supply & thermal drift rejection
z 14-pin TSSOP Pb-free package
mz Compatible with clear ITO over LCD construction
oz Inexpensive, simple 1-sided PCB construction possible
SNS3A
SNS2B
6
7
9 SNS1B
8 SNS2A
U.cAPPLICATIONS
y Personal electronics
y Appliance controls
y Climate controls
y Automotive controls
et4The QT411 QSlide™ IC is a new type of linear capacitive touch ‘slider’ sensor IC based on Quantum’s patented
charge-transfer (‘QT’) methods. This unique IC allows designers to create speed or volume controls, menu bars, and other
emore exotic forms of human interface on the panel of an appliance or personal electronic device. Generally it can be used to
replace any form of linear control, through a completely sealed panel.
hThe device uses a simple, inexpensive resistive sensing element between four connection points. The sense element can be a
straight line or curved. The device can report a single rapid touch anywhere along the sense element, or, it can track a finger
Smoving along the sensing surface in real time.
taThis device uses three channels of synchronous sensing across a resistive element to determine touch position, using
mathematical analysis. A positional accuracy of 5% (or better) is relatively easy to achieve. The acquisitions are performed in a
burst mode which uses proprietary spread-spectrum modulation for superior noise immunity and ultra-low RF low emissions.
aThe output of the QT411 can also be used to create discrete controls buttons in a line, by interpreting sets of number ranges
as buttons. For example, the number range 0..19 can be button A, 30..49 button B, 60..79 button C etc. Continuous slider
.Daction and number-range based discrete control points can be mixed on a single element, or, the element can be reinterpreted
differently at different times, for example when used adjacent to or on top of an LCD to act as a menu input device that
dynamically changes function in context. The device is compatible with ITO (Indium Tin Oxide) overlays on top of various
wdisplays or simply to provide for a backlighting effect.
The QT411 is significantly more stable with temperature and other environmental influences than the QT401 which it is
wdesigned to replace. In particular it can tolerate extreme temperature swings without false detection or shifts in reported touch
position. Also it does not require special calibration of the endpoints of the slider area. However, unlike the QT401 the QT411
wdoes not have a proximity detection function.
LQ
ataSheet4U.comCopyright © 2005 QRG Ltd
www.DQT411-ISSG R6.01/1005
1 page  
must be placed immediately over a ground plane within a
millimeter), the resistance might need to be lowered. Observe
the sensing pulses for flatness on their tops in the middle of a
segment using a small coin and scope probe to make sure
the pulses fully settle before the falling edge (see app note
AN-KD02 Figure 7).
The electrode can be made of a series chain of discrete
resistors with copper pads on a PCB, or from ITO (Indium Tin
Oxide, a clear conductor used in LCD panels and touch
screens) over a display. Thick-film carbon paste can also be
used, however linearity might be a problem as these films are
notoriously difficult to control without laser trimming or
scribing.
The linearity of the sensing strip is governed largely by the
linearity and consistency of the resistive element. Position
accuracy to within 5% is routinely achievable with good grade
resistors and a uniform construction method.
2.2 Cs Sample Capacitors
Cs1, Cs2 and Cs3 are the charge sensing sample capacitors;
normally they are identical in nominal value. They should be
of type X7R dielectric.
The optimal Cs values depend on the thickness of the panel
and its dielectric constant. Lower coupling to a finger caused
by a low dielectric constant and/or thicker panel will cause the
position result to become granular and more subject to
position errors. The ideal panel is made of thin glass. The
worst panel is thick plastic. Granularity due to poor coupling
can be compensated for by the use of larger values of sample
capacitors.
A table of suggested values for no missing position values is
shown in Table 1-2. Values of Cs smaller than those shown in
the table can cause skipping of position codes. Code skipping
may be acceptable in many applications where fine position
data is not required. Smaller Cs capacitors have the
advantage of requiring shorter acquisition bursts and hence
lower power drain.
Larger values of Cs improve granularity at the expense of
longer burst lengths and hence more average power.
Cs1, Cs2 and Cs3 should be X7R type, matched to within
10% of each other (ie, 5% tolerance) for best accuracy. The
PCB reference layout (Figure 1-3) is highly recommended. If
the Cs capacitors are poorly matched, position accuracy will
be affected and there could also be missing codes.
2.3 Rs Resistors
See Figure 1-1. Rs1, Rs2, and Rs3 are low value (typically
4.7K) resistors used to suppress the effects of ESD and
assist with EMC compliance. They are optional in most
cases.
In addition, there are two 8.2K resistors required to split
channel SNS3B into the two constituent ends. These two
resistors should be placed close to the ends of the slider
strip.
2.4 Power Supply
The usual power supply considerations with QT parts applies
also to the QT411. The power should be very clean and come
from a separate regulator if possible. This is particularly
critical with the QT411 which reports continuous position as
opposed to just an on/off output.
A ceramic 0.1µF bypass capacitor should be placed very
close to the power pins of the IC.
Regulator stability: Most low power LDO regulators have
very poor transient stability, especially when the load
transitions from zero current to full operating current in a few
microseconds. With the QT411 this happens when the device
comes out of sleep mode. The regulator output can suffer
from hundreds of microseconds of instability at this time,
which will have a negative effect on acquisition accuracy.
To assist with this problem, the QT411 waits 500µs after the
400µs taken to come out of sleep mode before acquiring to
allow power to fully stabilize. This delay is not present before
an acquisition burst if there is no preceding sleep state.
Use an oscilloscope to verify that Vdd has stabilized to within
5mV or better of final settled voltage before a burst begins.
The QT411 has specially enhanced power supply rejection
built in. This means that it is often possible to share the
regulator with other circuits. However, it is always advised to
be sure that Vdd is free from spikes and transients, and is
filtered sufficiently to prevent detection problems.
During development it is wise to first design a regulator onto
the PCB just for (and next to) the QT411, but allow for it to be
‘jumpered out’. If in development it is clear that there are no
problems with false detection or ‘angle noise’ even without a
separate regulator for the QT411, then the regulator can be
safely omitted.
2.5 PCB Layout and Mounting
One form of PCB layout is shown in Figure 1-3. This is a
1-sided board; the blank side is simply adhered to the inside
of a 2mm thick (or less) control panel. Thicker panels can be
tolerated with additional position error due to capacitive ‘hand
shadow’ effects and will also have poorer EMC performance.
The Figure 1-3 layout uses a series copper pads connected
with intervening series resistors in a row. The total resistance
between any two connection points can be in the range of
100K to 500K, with ~400K being a suitable target value .
Resistance values at the higher end of this range will
generate more sensitivity provided there is no ground plane
close underneath the electrode strip.
A human finger interpolates between the copper pads (if the
pads are narrow enough) to make a smooth output with no
apparent steps. The lateral dimension along the centre of
each electrode should be no wider than the expected
smallest diameter of finger touch, to prevent stepping of the
position response (if it matters).
It is also possible create an interleaved electrode array with
only 3 resistors between each channel’s connection point on
the strip. Interleaving eliminates stepping while reducing the
number of required resistors. Consult Quantum for further
details.
Resistive inks (such as ITO, Agfa OrgaconTM etc.) can also be
used if the resistance between connection points is in the
recommended range.
The electrode strip can be made in various lengths up to at
least 80mm. The electrode width should be about 12mm wide
or more, as a rule. The strip can also be an arc or other
irregular shape. For a 360 degree wheel, use the QT511 or
consult Quantum for other options.
lQ
5 QT411-ISSG R6.01/1005
5 Page 
4.6 TSSOP Package
E
E1
n
B
D
2
1
A
a
c A1
L
Units
Dimension Limits
Number of Pins
Pitch
Overall Height
S t andoff
Overall W idth
Moulded Package W idth
Moulded Package Length
Foot Length
Foot Angle
Lead Thickness
Lead W idth
Mould Draft Angle Top
Mould Draft Angle Bottom
n
p
A
A1
E
E1
D
L
c
B
a
M IN
0.002
0.246
0.169
0.193
0.020
0
0.004
0.007
0
0
INCHE S
NOM
14
0.026
0.004
0.251
0.173
0.197
0.024
4
0.006
0.010
5
5
MAX
0.043
0.006
0.256
0.177
0.201
0.028
8
0.008
0.012
10
10
M ILLIM E TE RS
M IN
NOM
MAX
14
0.65
1.10
0.05
0.10
0.15
6.25
6.38
6.50
4.30
4.40
4.50
4.90
5.00
5.10
0.50
0.60
0.70
048
0.09
0.15
0.20
0.19
0.25
0.30
0 5 10
0 5 10
4.7 Ordering Information
PART NO.
QT411-ISSG
PACKAGE
TSSOP-14
TEMP RANGE
-400C ~ +850C
MARKING
QT411
lQ
11 QT411-ISSG R6.01/1005
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet QT411-ISSG.PDF ] | |
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