QT1106 View Datasheet(PDF) - Quantum Research Group
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QT1106 Datasheet PDF : 20 Pages
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1.7 Basic Power Modes
1.7.1 Overview
The device features a number of modes to set the current
drain and speed of response.
The available operating modes are:
# Free Run - fastest detection response at all times
# LP mode - low power, slower touch sensing response
# Sleep - microamp-level current drain
# Sync mode - for noise suppression of low frequencies
1.7.2 Free Run Mode
This mode uses a continuous stream of acquire bursts . Free
Run mode has, in consequence, t he highest power drain of
all the QT1106 operating modes but the fastest response
time.
1.7.3 LP Mode
In LP (low power) mode, the QT1106 spends most of the
time sleeping to conserve power; it wakes itself periodically
to perform acquire bursts, then normally goes back to sleep
again.
The QT1106 provides a choice of intervals between acquire
bursts to allow an appropriate speed /power trade-off to be
made for each product.
1.7.4 Sleep Mode
In Sleep mode, the QT1106 shuts down to conserve power;
it will remain in this mode forever or unti l the host wakes it
using the /SS pin.
1.7.5 Sync Mode
In this mode the device will synchronize to the host in a way
that allows for the suppression of heavy low frequency noise;
for example, from mains frequencies and their harmonics.
2 Signal Processing
2.1 Power-up Self-calibration
On power-up or after reset, all 10 channels are typically
calibrated and operational within 650ms.
2.2 Drift Compensation
This operates to correct the reference level of each key
automatically over time; it suppresses false detections
caused by changes in temperature, humidity, dirt and other
environmental effects.
2.3 Detection Integrator Filter
Detect Integrator (DI) filter confirmation reduces the effects
of noise on key states. The DI mechanism requires a
specified number of measurements that qualify as detections
(and these must occur in a row) or the detection will not be
reported.
In a similar manner, the end of a touch (loss of signal) also
has to be confirmed over several measurements. The
QT1106 provides a choice of either two or six DI
measurements for confirming start of touch; end of touch
always uses two measurements.
The DI mechanism works together with spread spectrum
operation to dramatically reduce the effects of noise.
2.4 AKSTM Adjacent Key Suppression
This patented feature works to prevent multiple keys from
responding to a single touch . This can happen with closely
spaced keys, or a scroll wheel that has buttons very near it.
AKS operates by comparing signal strengths from keys
within a group of keys to suppress touch detections from
those that have a weaker signal change than the dominant
one.
When enabled globally on the QT1106, AKS allows only one
independent key, or the scroll section , to indicate a touch at
a time. Additionally, the QT1106 has options for partial AKS ;
where some keys are included in the AKS operation and
others are not affected. In this case only one key in the AKS
group can indicate a touch at any time; other keys can
indicate touch in any combination.
AKS can also be disabled.
2.5 Autorecalibration (MOD)
The device can time out and recalibrate each key
independently after a continuous touch detection that lasts
for the chosen ‘Maximum on-duration’ (MOD). This ensures
that a key can never become ‘stuck on’ due to foreign
objects or other external influences.
After recalibration the key will continue to function normally.
The nominal delay is selectable to be either 10s, 20s, 60s, or
infinite (disabled), though the actual delay is different in
some operating modes (see Table 2.1).
Table 2.1 Maximum On-duration
Operating Mode
Free Run
LP mode,
200ms1 response (120ms2)
LP mode,
280ms1 response (200ms2)
LP mode,
440ms1 response (360ms2)
LP mode,
760ms1 response (680ms2)
Sync mode
(typ 55Hz sync)
Sleep mode
Max on-durations
10s, 20s, 60s
10s, 20s, 60s
10s, 20s, 60s
15s, 30s, 88s
28s, 55s, 164s
10s, 20s, 60s
(vary with sync rate)
n/a
1 response times are estimated using a DI of six counts.
2 response times are estimated using a DI of two counts.
Note: all response times are based on typical sense
capacitor values.
The device also autorecalibrates all keys when one or more
normal keys’ signal reflect a sufficient decrease in
capacitance from the reference level (signal error). If QMagic
Proximity mode is active, a signal error on the Proximity Key
(Key 7) will only recalibrate itself. This is filtered in a manner
similar to the DI filter; the decrease in capacitance must be
seen for at least six successive cycles. Hence, in Free Run
mode the device typically recalibrates within 400ms so as to
recover normal operation quickly.
Lq
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QT1106-ISG R8I.05/0906
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