QST608 ST Microelectronics, QST608 Datasheet - Page 13

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

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QST608
4.2
4.3
Note:
1
Reset and power-up
At power-up, the device configures itself according to the ADD[2:0] option resistors. The
device start-up and configuration may take up to t
When the power is established, it is possible to force a new device configuration by applying
a negative pulse on the RESET pin.
The RESET pin is a bidirectional pin with an internal pull-up. The line is forced low when the
device resets itself (through an I²C command, for example).
A 10nF capacitor is recommended on the RESET pin to ensure reliable start-up and noise
immunity.
Burst operation
The device operates in “Burst” mode. Each key touch is acquired using a burst of charge-
transfer sensing pulses whose count varies depending on the value of the sense capacitor
C
of pulses:
●
●
●
Bursts always operate in an A-B-C sequence. If all keys belonging to a same burst are not
implemented, the QST device will not perform the Burst in order to improve the response
time and reduce the power consumption when in Low Power (LP) mode.
In Low Power mode, the device sleeps in an ultra-low current state between bursts to reduce
power consumption.
If you decide to use a rotor with a center dome button, Key 5 must be used.
S
and the load capacitance C
Burst A: Keys 1 to 4
Burst B: Keys 5
Burst C: R1, R2 and R3 (for rotor or slider)
X
. Key touches are acquired using several successive bursts
Setup
.
Device operating mode
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