QT60160-ISG Atmel, QT60160-ISG Datasheet - Page 18

• Manufacturer Part Number: QT60160-ISG
• Description: SENSOR IC MTRX TOUCH16KEY 32-QFN
• Manufacturer: Atmel
• Series: QMatrix™r
• Type: Capacitiver

Specifications of QT60160-ISG

• Number Of Inputs/keys: 16 Key
• Resolution (bits): 10 b
• Data Interface: I²C, Serial, SPI™
• Voltage Reference: External
• Voltage - Supply: 1.8V, 3.3V, 5V
• Current - Supply: 4.6mA
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 32-MLF®, QFN
• Output Type: *
• Interface: *
• Input Type: *
• Operating Supply Voltage: 1.8 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 427-1125-2

Specifically, drift compensation should be set to compensate
faster for increasing signals than for decreasing signals.
Decreasin g 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, 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.
Drift compensation and the detection time-outs 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'.
NDRIFT Typical values:
NDRIFT Default value:
PDRIFT Typical values:
PDRIFT Default value:
6.5 Detect Integrators - NDIL, FDIL
NDIL is used to enable or disable keys and to provide
signal filtering. To enable a key, its NDIL parameter should
be nonzero (ie NDIL=0 disables a key). See Section 2.2.
To suppress false detections caused by spurious events
like electrical noise, the devices incorporate a 'detection
integrator' or DI counter mechanism. A per-key counter is
incremented each time the key has exceeded its threshold
and stayed there for a number of acquisitions in
succession, without going below the threshold level. When
this counter reaches a preset limit the key is finally
declared to be touched.
If on any acquisition the signal is not seen to exceed the
threshold level, the counter is cleared and the process has
to start from the beginning.
The DI mechanism uses two counters. The first is the ‘fast
DI’ counter FDIL. When a key’s signal is first noted to be
below the negative threshold, the key enters ‘fast burst’
mode. In this mode the burst is rapidly repeated for up to
the specified limit count of the fast DI counter. Each key
has its own counter and its own specified fast-DI limit
(FDIL), which can range from 1 to 15. When fast-burst is
entered the QT device locks onto the key and repeats the
acquire burst until the fast-DI counter reaches FDIL, or, the
detection fails beforehand. After this the device resumes
normal keyscanning and goes on to the next key.
The ‘Normal DI’ counter counts the number of times the
fast-DI counter reached its FDIL value. The Normal DI
counter can only increment once per complete scan of all
keys. Only when the Normal DI counter reaches NDIL does
the key become formally ‘active’.
The net effect of this is that the sensor can rapidly lock
onto and confirm a detection with many confirmations,
while still scanning other keys. The ratio of ‘fast’ to ‘normal’
counts is completely user-settable via the Setups process.
The total number of required confirmations is equal to FDIL
times NDIL.
lQ
(2 to 3.3 seconds per count of drift compensation)
(2.5s / count of drift compensation)
(0.4 to 0.8 seconds per count of drift compensation;
translation via LUT, page )
(0.6s / count of drift compensation)
9 to 11
10
3 to 5
4
18
If FDIL = 5 and NDIL = 2, the total detection confirmations
required is 10, even though the device only scanned
through all keys only twice.
The DI is extremely effective at reducing false detections at
the expense of slower reaction times. In some applications
a slow reaction time is desirable . The DI can be used to
intentionally slow down touch response in order to require
the user to touch longer to operate the key.
If FDIL = 1, the device functions conventionally . Each
channel acquires only once in rotation , and the normal
detect integrator counter (NDIL) operates to confirm a
detection. Fast-DI is in essence not operational.
If FDIL m 2, then the fast-DI counter also operates in
addition to the NDIL counter.
If Signal [ NTHR: The fast-DI counter is incremented
towards FDIL due to touch.
If Signal >NTHR then the fast-DI counter is cleared due to
lack of touch.
Disabling a key: If NDIL =0, the key becomes disabled.
Keys disabled in this way are pared from the burst
sequence in order to improve sampling rates and thus
response time. See Section 2.2, page 3.
NDIL Typical values:
NDIL Default value:
FDIL Typical values:
FDIL Default value:
6.6 Negative Recal Delay - NRD
If an object unintentionally contacts a key resulting in a
detection for a prolonged interval it is usually desirable to
recalibrate the key in order to restore its function , perhaps
after a time delay of some seconds.
The Negative Recal Delay timer monitors such detections;
if a detection event exceeds the timer's setting, the key will
be automatically recalibrated. After a recalibration has
taken place, the affected key will once again function
normally even if it is still being contacted by the foreign
object. This feature is set on a per-key basis using the
NRD setup parameter.
NRD can be disabled by setting it to zero (infinite timeout)
in which case the key will never auto-recalibrate during a
continuous detection (but the host could still command it).
NRD is set using one byte per key, which can range in
value from 0...254. NRD above 0 is expressed in 0.5s
increments. Thus if NRD =120, the timeout value will
actually be 60 seconds. 255 is not a legal number to use.
NRD Typical values:
NRD Default value:
NRD Range:
NRD Accuracy:
6.7 Positive Recalibration Delay - PRD
A recalibration occurs automatically if the signal swings
more positive than the positive threshold level. This
condition can occur if there is positive drift but insufficient
positive drift compensation , or, if the reference moved
negative due to a NRD auto-recalibration, and thereafter
the signal rapidly returned to normal (positive excursion).
QT60240-ISG R8.06/0906
20 to 60 (10 to 30 seconds)
20 (10 seconds)
0..254 (∞, 0.5...127s)
to within ± 250ms
2, 3
2
4 to 6
5