QST608 ST Microelectronics, QST608 Datasheet - Page 14

• Manufacturer Part Number: QST608
• Description: Capacitive touch sensor device
• Manufacturer: ST Microelectronics

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Device operating mode
4.4
Caution:
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Low power mode
In order to reduce the device power consumption, the QST family include scalable low
power modes.
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If an I
not acknowledge the frame (even if it has an I
must therefore send again the frame until it is taken in account and acknowledged.
Internal device frequency
The internal device frequency can be modified to better adapt to the device low power
mode usage and I
Only two speeds are available: maximum frequency and reduced frequency.
Standard low power mode
When the device is in standard low power mode, a window with very low power
consumption is inserted between the acquisition of the last active key and the following
acquisition of the first active key.
This window duration is programmable as the 'sleep duration time'.
Note that the sleep window insertion is cancelled in the following conditions:
–
–
–
Free run in detect
The behavior in this mode is the same as in the standard low power mode except that
the sleep window insertion is always skipped if any of the active keys is detected as
touched.
This is useful to improve the wheel response time.
Deep Sleep mode
In deep sleep mode, the device enters a very low power mode indefinitely. The device
resumes its operations after receiving an I
2
C frame is received while in sleep or deep sleep mode, the device wakes up but does
If a change is detected on a key, in order to speed up the DI process, the sleep
window insertion is skipped until the end of the DI process.
When a key change is actually detected and reported with a negative pulse on the
IRQ pin. In this case, the low power mode is disabled until a command is received
from the host.
Inside an I
period is skipped.
2
C command, between the Write and the Read I
2
C speed.
2
C frame with the device address). The host
2
C frame with the device address or a reset.
2
C frames, the sleep
QST608