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PDF QT511-ISSG Data sheet ( Hoja de datos )
| Número de pieza | QT511-ISSG | |
| Descripción | QWHEEL TOUCH SLIDER IC | |
| Fabricantes | QUANTUM | |
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LQ
QT511-ISSG
QWHEEL™ TOUCH SLIDER IC
z Rotary finger-touch ‘wheel’ slider control
z Center-button compatible signal processing
z Extremely simple circuit - no external active components
z SPI slave-mode interface
z Self-calibration and drift compensation
z Spread-spectrum operation for optimal EMC compliance
z 2.5 - 5.5V single supply operation; very low power
z Enhanced power supply & thermal drift rejection
z 14-pin TSSOP Pb-free package
z Compatible with clear ITO over LCD construction
z Inexpensive, simple 1-sided PCB construction possible
z Reference design board available
VDD
SDO
/SS
SCLK
SNS3B
SNS3A
SNS2B
1 14
2 13
3 QT511 12
4 11
5 10
69
78
GND
DRDY
DETECT
SDI
SNS1A
SNS1B
SNS2A
APPLICATIONS
y Personal electronics
y Appliance controls
y Shaft encoders
y Automotive controls
The QT511 QSlide™ IC is a new type of rotary capacitive touch ‘slider’ sensor IC based on Quantum’s patented
charge-transfer methods. This unique IC allows designers to create speed or volume controls, menu bars, and other more
exotic forms of human interface on the panel of an appliance. Generally it can be used to replace any form of rotary knob,
through a completely sealed panel.
The device uses a simple, inexpensive resistive sensing element between three connection points. The sense element can be
circular or any polygon shape.
The QT511 can report a single rapid touch anywhere along the sense element, or, it can track a finger moving along the wheel
surface in real time. The device self-calibrates under command from a host controller.
This device uses three channels of simultaneous sensing across a resistive element to determine finger 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 low emissions.
The output of the QT511 can also be used to create discrete controls in a circle, 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 wheel action
and discrete controls can be mixed on a single element, or, the element can be reinterpreted differently at different times, for
example when used below 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 displays or simply to provide for a backlighting
effect.
The QT511 has two enhancements over the QT510. It is significantly more stable with temperature and other environmental
influences, and it recognizes a touch in the middle of the wheel as being invalid, which aids considerably in placing a touch
button in the center of the wheel. However, unlike the QT510 the QT511 does not have a proximity detection function.
LQ
Copyright © 2005 QRG Ltd
QT511-ISSG R6.01/1005
1 page  
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, the wheel accuracy will
be affected and there could also be missing codes.
2.3 Rs Resistors
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 many cases.
During development it is wise to first design a regulator onto
the PCB just for (and next to) the QT511, 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
regulator just for the QT511, then the regulator can be safely
omitted.
2.5 PCB Layout and Mounting
The E510 PCB layout (Figure 1-3) should be followed if
possible. 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.
This layout uses 18 copper pads connected with intervening
series resistors in a circle. The finger interpolates between
the copper pads (if the pads are narrow enough) to make a
smooth, 0..127 step output with no apparent stair-casing. The
lateral dimension along the centre of each electrode should
be no wider than the expected smallest diameter of finger
touch, to prevent stair-casing of the position response (if that
matters).
Other geometries are possible, for example triangles and
squares. The wheel can be made in various diameters up to
at least 80mm. The electrode width should be about 12mm
wide or more, as a rule.
The SMT components should be oriented perpendicular to
the direction of bending so that they do not fracture when the
PCB is flexed during bonding to the panel.
Additional ground area or a ground plane on the PCB will
compromise signal strength and is to be avoided. A single
sided PCB can be made of FR-2 or CEM-1 for low cost.
2.4 Power Supply
The usual power supply considerations with QT parts applies
also to the QT511. The power should be very clean and come
from a separate regulator if possible. This is particularly
critical with the QT511 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 QT511 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 QT511 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.
‘Handshadow’ effects: With thicker and wider panels an
effect known as ‘handshadow’ can become noticeable. If the
capacitive coupling from finger to electrode element is weak,
for example due to a narrow electrode width or a thick, low
dielectric constant panel, the remaining portion of the human
hand can contribute a significant portion of the total
detectable capacitive load. This will induce an offset error,
which will depend on the proximity and orientation of the hand
to the remainder of the element. Thinner panels and those
with a smaller diameter will reduce this effect since the finger
contact surface will strongly domina te the total signal, and the
remaining handshadow capacitance will not contribute
significantly to create an error offset.
PCB Cleanliness: All capacitive sensors should be treated
as highly sensitive circuits which can be influenced by stray
conductive leakage paths. QT devices have a basic
resolution in the femtofarad range; in this region, there is no
such thing as ‘no clean flux’. Flux absorbs moisture and
becomes conductive between solder joints, causing signal
drift and resultant false detections or temporary loss of
sensitivity. Conformal coatings will trap in existing amounts of
moisture which will then become highly temperature
sensitive.
The QT511 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.
The designer should specify ultrasonic cleaning as part of the
manufacturing process, and in extreme cases, the use of
conformal coatings after cleaning.
lQ
5 QT511-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.
QT511-ISSG
PACKAGE
TSSOP-14
TEMP RANGE
-400C ~ +850C
MARKING
QT511
lQ
11 QT511-ISSG R6.01/1005
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet QT511-ISSG.PDF ] | |
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