QT1106 Ver la hoja de datos (PDF) - Quantum Research Group
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QT1106 Datasheet PDF : 20 Pages
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Command During LP Mode: First read ‘/SS Wake Pulse in
LP Mode’, on Page 11. Following DRDY rising at the end of
the 45µs low pulse, the host may perform a normal SPI
transfer as shown in Figure 3.1. The SPI transfer may start
while DRDY is high (450µs), and for a 20µs grace period
thereafter.
After the SPI transfer is completed, the QT1106 will generate
a set of three acquire bursts if LPB=1, during which DRDY
will be low.
The mode and options settings sent from the host to the
QT1106 during the SPI transfer take effect after the set of
acquire bursts.
# If Free Run mode is selected, the QT110 6 will take
DRDY high to indicate the possibility of an SPI transfer.
# If either LP mode or Sleep mode is selected, the
QT1106 will go back to sleep with DRDY high provided
no key is detected as possibly touched.
# If Sync mode is selected, the QT1106 will go back to
sleep with DRDY high provided no key is detected as
possibly touched.
The CHANGE pin will go high at this time if a key is
confirmed as touched.
4.4 Sleep Mode
Sleep mode offers the lowest possible current drain, in the
low microamp region.
Sleep mode is a special case of LP mode, where the sleep
duration between bursts is infinite. All comments concerning
LP mode, including about SPI communications , apply
equally to Sleep mode, except that the LPB bit is ignored
and bursts are always generated after an SPI transfer or
/SS wake pulse as if LPB=1.
Note that in Sleep mode the QT1106 only performs
acquisition bursts following being woken by /SS. This has
two effects.
# Touch detection only occurs following /SS-wake pulses,
and hence CHANGE can only go high at that time.
# The QT1106 cannot drift its internal references unless
the host sends periodic /SS wake pulses. If the host
does not do this, then it should command the QT110 6 to
recalibrate when it sets the QT1106 into a different
operating mode.
This mode can be used by the host to create its own ‘LP
Mode’ timings via the /SS wakeup pulse method.
4.5 Sync Mode
This mode is useful for low frequency noise suppression, for
example from mains frequencies in line-operated appliances.
Acquisition bursts are synchronized to the /SS-wake pulses
from the host.
Sync mode is very similar to ‘LP 760ms response time’
mode, with two differences:
# It does not operate as in Free Run mode when a touch
is first detected
# The LPB bit is ignored and a burst is always generated
after each /SS wakeup or SPI transfer as if LPB=1
Not operating as in Free Run mode when a touch is first
detected (before DI confirmation has taken place) means
that acquisition bursts are restricted to the immediate time
after a sync signal (/SS), heightening the effect of low
frequency noise suppression.
In many applications of Sync mode the DI filter will need to
be set to two counts, to avoid the QT1106 response time
being unacceptably lengthened as a consequence of this.
Figure 4.2 LP Mode SPI Operation with LPB=0
Acquire Bursts
No SPI Communication
>40us
<150us
DRDY from QT
<100us
/SS from host
>125us
SPI Communication
>70us
<200us
<470us
/SS timing as left
SCLK from Host
don't care
Host Data Output
(QT1106 Input - MOSI)
don't care
QT Data Output
(QT1106 Out - MISO)
3-state
don't care
don't care
don't care
command bytes
response bytes
don't care
3-state
Lq
12
QT1106-ISG R8I.05/0906
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