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QT60485B Schematic ( PDF Datasheet ) - QUANTUM

Teilenummer QT60485B
Beschreibung (QT60325B - QT60645B) QMatrix KEYPANEL SENSOR ICS
Hersteller QUANTUM
Logo QUANTUM Logo 




Gesamt 30 Seiten
QT60485B Datasheet, Funktion
www.DataSheet4U.com
LQ
QT60325B, QT60485B, QT60645B
32, 48, 64 KEY QMatrixKEYPANEL SENSOR ICS
Advanced second generation QMatrix controllers
Up to 32, 48 or 64 touch keys through any dielectric
Panel thicknesses to 5 cm or more
100% autocal for life - no adjustments required
Keys individually adjustable for sensitivity, response time,
and many other critical parameters
Mix and match key sizes & shapes in one panel
Passive matrix - no components at the keys
Moisture suppression capable
AKS™ - Adjacent Key Suppression feature
Synchronous noise suppression
Sleep mode with wake pin
SPI Slave or Master/Slave interface to a host controller
Low overhead communications protocol
44-pin TQFP package
MOSI
MISO
SCLK
RST
Vdd
Vss
XTO
XTI
X0
X1
X2WS
44 43 42 41 40 39 38 37 36 35 34
1 33
2 32
3 31
4 QT60325B 30
5 QT60485B 29
6 QT60645B 28
7 27
8
9
TQFP-44
26
25
10 24
11 23
12 13 14 15 16 17 18 19 20 21 22
CZ2
YS0
YS1
YS2
Aref
AGnd
AVdd
YC7
YC6
YC5
YC4
APPLICATIONS
Security keypanels
Industrial keyboards
Appliance controls
Outdoor keypads
ATM machines
Touch-screens
Automotive panels
Machine tools
The QT60325B, QT60485B, and QT60645B digital charge-transfer (“QT”) QMatrix™ ICs are designed to detect human touch on
up to 32, 48, or 64 keys respectively using a scanned, passive X-Y matrix. It will project the keys through almost any dielectric, e.g.
glass, plastic, stone, ceramic, and even wood, up to thicknesses of 5 cm or more. The touch areas are defined as simple 2-part
interdigitated electrodes of conductive material, like copper or screened silver or carbon deposited on the rear of a control panel.
Key sizes, shapes and placement are almost entirely arbitrary; sizes and shapes of keys can be mixed within a single panel of
keys and can vary by a factor of 20:1 in surface area. The sensitivity of each key can be set individually via simple functions over
the SPI port, for example via Quantum’s QmBtn program. Key setups are stored in an onboard eeprom and do not need to be
reloaded with each power-up.
These ICs are designed specifically for appliances, electronic kiosks, security panels, portable instruments, machine tools, or
similar products that are subject to environmental influences or even vandalism. They permit the construction of 100% sealed,
watertight control panels that are immune to humidity, temperature, dirt accumulation, or the physical deterioration of the panel
surface from abrasion, chemicals, or abuse. To this end the devices contain Quantum-pioneered adaptive self-calibration, drift
compensation, and digital filtering algorithms that make the sensing function robust and survivable. The devices use short dwell
times and Quantum’s patent-pending AKS™ feature to permit operation in wet environments.
The parts use a passive key matrix, dramatically reducing cost over older technologies that require an ASIC for every key. The
key-matrix can be made of standard flex material (e.g. Silver on PET plastic) or ordinary PCB material to save cost.
External circuitry consists of an opamp, R2R ladder-DAC network, a common PLD, a FET switch, and a small number of resistors
and capacitors which can fit into a footprint of roughly 8 sq. cm (1.5 sq. in). Control and data transfer is via a SPI port which can
be configured in either a Slave or Master/Slave mode.
QT60xx5B ICs make use of an important new variant of charge-transfer sensing, transverse charge-transfer, in a matrix format
that minimizes the number of required scan lines to provide a high economy of scale.
The B version is identical to the earlier QT60xx5 parts in all respects except that the device exhibits lower signal noise.
QT60xx5B replaces QT60xx5 parts with no circuit changes. After 2003, QT60xx5 devices will no longer be available.
lQ
AVAILABLE OPTIONS
TA
-400C to +1050C
-400C to +1050C
-400C to +1050C
TQFP
QT60325B-AS
QT60485B-AS
QT60645B-AS
Copyright © 2001 Quantum Research Group Ltd
Pat Pend. R1.06/0403






QT60485B Datasheet, Funktion
© Quantum Research Group Ltd.
the detection integrator (Section 2.6). Larger absolute values
of threshold desensitize keys since the signal must travel
farther in order to cross the threshold level. Conversely, lower
thresholds make keys more sensitive.
As Cx and Cs drift, the reference point drift-compensates for
these changes at a user-settable rate (Section 2.4); the
threshold level is recomputed whenever the reference point
moves, and thus it also is drift compensated.
The negative threshold is programmed on a per-key basis
using the setup process described in Section 5.
2.2 Positive Threshold
See also command ^B, page 24
The positive threshold is used to provide a mechanism for
recalibration of the reference point when a key's signal moves
abruptly to the positive. These transitions are described more
fully in Section 2.7.
Positive threshold levels are programmed in using the setup
process described in Section 5 on a per-key basis.
when the signal in question has not crossed the negative
threshold level (Section 2.1).
The drift compensation mechanism can be made asymmetric
if desired; the drift-compensation can be made to occur in
one direction faster than it does in the other simply by setting
^H and ^I to different settings.
Specifically, drift compensation should be set to compensate
faster for increasing signals than for decreasing signals.
Decreasing signals should not be compensated quickly, since
an approaching finger could be compensated for partially or
entirely before even touching the touch pad. However, an
obstruction over the sense pad, for which the sensor has
already made full allowance for, could suddenly be removed
leaving the sensor with an artificially suppressed reference
level and thus become insensitive to touch. In this latter case,
the sensor should compensate for the object's removal by
raising the reference level relatively quickly.
The drift compensation rate can be set for each key
individually, and can also be disabled completely if desired on
a per-key basis.
2.3 Hysteresis
See also command ^C and ^D, page 25
Refer to Figure 2-1. QT60xx5B ICs employ programmable
hysteresis levels of 12.5%, 25%, or 50% of the delta between
the reference and threshold levels. There are different
hysteresis settings for positive and negative thresholds which
can be set by the user. The hysteresis is a percentage of the
distance from the threshold level back towards the reference,
and defines the point at which the detection will drop out. A
percentage of 12.5% is less hysteresis than 25%, and the
12.5% hysteresis point is closer to the threshold level than to
the reference level.
Drift compensation and the detection time-outs (Section 2.5)
work together to provide for robust, adaptive sensing. The
time-outs provide abrupt changes in reference calibration
depending on the duration of the signal 'event'.
Drift compensation can result in reference levels that are at
the boundaries of the 8-bit signal window. When this occurs,
saturation is reached and the drift compensation process
stops. One of two error flags is set when the signal
approaches either end of the signal window; it is up to the
host to read these flags and induce a full recalibration via a
recalibration command at that time (Section 2.10 and
command b, page 28) for the key in question.
The hysteresis levels are set for all keys only; it is not
2.5 Detection Recalibration Delay
possible to set the hysteresis differently from key to key on See also command ^L, page 26
either the positive or negative hysteresis levels.
If a foreign object contacts a key the key's signal may change
2.4 Drift Compensation
enough in the negative direction, the same as a normal
touch, to create an unintended detection. When this happens
See also commands ^H, ^I, page 26
it is usually desirable to cause the key to be recalibrated in
Signals can drift because of changes in Cx and Cs over time
and temperature. It is crucial that such drift be compensated,
order to restore its function after a time delay of some
seconds.
else false detections and sensitivity shifts can occur. The
The Negative Recal Delay timer monitors this detection
QT60xx5B compensates for drift using setups, ^H and ^I.
duration; if a detection event exceeds the timer's setting, the
Drift compensation (Figure 2-1) is performed by making the
reference level track the raw signal at a slow rate, but only
while there is no detection in effect. The rate of adjustment
must be performed slowly, otherwise legitimate
detections could be ignored. The devices drift
compensate using a slew-rate limited change to
key will be fast-recalibrated within its current 8-bit window.
This form of recalibration is simply one of setting Reference =
Signal, and does not affect Offset or Cz state; as a result this
form of recalibration requires only one burst spacing interval
t
Figure 2-1 Thresholds and Drift Compensation
the reference level; the threshold and hysteresis
values are slaved to this reference.
When a finger is sensed, the signal falls since the
human body acts to absorb charge from the
cross-coupling between X and Y lines. An isolated,
untouched foreign object (a coin, or a water film)
will cause the signal to rise very slightly due to an
enhancement of coupling. This is contrary to the
way most capacitive sensors operate.
Once a finger is sensed, the drift compensation
mechanism ceases since the signal is legitimately
detecting an object. Drift compensation only works
Hysteresis
Threshold
Output
Reference
Signal
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6 www.qprox.com QT60xx5B / R1.06

6 Page









QT60485B pdf, datenblatt
© Quantum Research Group Ltd.
Figure 3-3 Relationship of X and Y signals
'n' pulses / burst
R 2 R Value
Xa
3.5.2 NOISE COUPLING INTO Y LINES
External noise, sometimes caused by ground bounce due to
injected line noise, can couple into the Y lines and cause
signal interference in extreme cases. Such noise can be
readily suppressed by adding a 100pF capacitor from each Y
line to a ground plane near the QT60xx5B.
Yb
Amp out
3.6 Burst Length & Sensitivity
See also Command ^F, page 25
The signal gain in volts / pF of Cx for each key is controlled
by circuit parameters as well as the burst length.
The burst length is simply the number of times the
charge-transfer (QT) process is performed on a given key.
Xa Each QT process is simply the pulsing of an X line once, with
a corresponding Y line enabled to capture the resulting
Yb charge passed through the keys capacitance Cx.
Yb'
Yb
3.4.2 NOISE COUPLING INTO X LINES
External noise, sometimes caused by ground bounce due to
injected line noise, can couple into the X lines and cause
signal interference in extreme cases. Such noise can be
readily suppressed by the use of series resistors as
described above. Adding a small capacitor to the matrix line
on the QT60xx5B side of the R, for example 100pF to ground
near the QT60xx5B, will greatly help to reduce such effects.
3.5 'Y' Gate Drives
There are 8 'Y' gate drives (YC0..YC7) which are active-high;
only one of these lines is used during a burst for a particular
key. These lines are used to control the PLD to ground all
unselected Ylines, making them low impedance. The
selected Yline in the matrix remains unclamped by the PLD
during the rising edge of the Xdrive line, during the time that
the coupled charge from a single key is fed to the charge
integrator via the 8:1 analog mux.
There are also 3 Y-encoded lines YS0..YS2 which select the
correct switch to actuate in the analog mux for the desired Y
line. Line YGfrom the controller acts to trigger the PLDs
pulse generation circuit, whose pulse width following the rise
of an Xline is dependent on an RC time constant. This
pulse, YE, drives the enable pin of the QS3251 mux low
(switch on) just before a positive-going Xdrive pulse, and
high again (switch off) just after the Xdrive pulse. The time
from the rising edge of an Xsignal to the rising edge of YE
is referred to as the dwell time, and this parameter has a
direct effect on the ability of the circuit to suppress moisture
films (see Sections 3.9 and 3.13).
After the YEpulse has ceased, the controller and circuit act
to ground all Ylines via the PLD just before the Xdrive
signal goes low; this restores the charge across the matrix
keys to a null state, making them ready for another sample.
QT60xx5B devices use a finite number of QT cycles which
are executed in a short burst. There can be from 1 to 64
cycles in a burst, in accordance with the list of permitted
values shown for command ^F, page 25. If burst length is set
to zero, the burst is disabled but its time slot in the scanning
sequence of all keys is preserved so as to maintain uniform
timing.
Increasing burst length directly affects key sensitivity. This
occurs because the accumulation of charge in the charge
integrator is directly linked to the burst length. The burst
length of each key can be set individually, allowing for direct
digital control over the signal gains of each key individually.
Apparent touch sensitivity is also controlled by Negative
Threshold (Section 2.1). Burst length and negative threshold
interact; normally burst lengths should be kept as short as
possible to limit RF emissions, but the threshold setting
should be kept above a setting of 6 to limit false detections.
The detection integrator can also prevent false detections at
the expense of slower reaction time (Section 2.6).
3.7 Intra-Burst Spacing
See also Command ^M, page 27
The time between X drive pulses during a burst is the
intra-burst pulse spacing. This timing has no noticeable effect
on performance of the circuit, but can have an impact on the
nature of RF spectral emissions from the matrix panel. The
setting of this function can be from 2µs through 10µs, loosely
corresponding to fundamental emission frequencies from
500kHz and 100kHz respectively.
Longer spacings require more time to execute and can limit
the operational settings of burst length and/or burst spacing
(Section 5.7).
The intra-burst QT spacing has no effect on sensitivity or
water film suppression and is not particularly important to the
sensing function other than described above.
3.8 Burst Spacing
See also Command ^G, page 25
3.5.1 RFI FROM Y LINES
Y lines are 'virtual grounds' and do not radiate a significant
amount of RFI; in fact, they act as sinksfor RFI emitted by
the X lines since they are virtual grounds. Series-R in the Y
lines is not required for RFI suppression, and in fact series-R
can introduce cross-talk among keys.
The interval of time from the start of one burst to the start of
the next is known as the burst spacing. This is an alterable
parameter which affects all keys.
Shorter spacings result in faster response time, but due to
increasing timing restrictions at shorter spacings burst
lQ
12 www.qprox.com QT60xx5B / R1.06

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