at42qt2100 ATMEL Corporation, at42qt2100 Datasheet - Page 18

• Manufacturer Part Number: at42qt2100
• Description: Qtouch Touch Sensor Ic
• Manufacturer: ATMEL Corporation

4.4.4
18
AT42QT2100
Sleep Mode
Figure 4-2.
Note:
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 QT2100 only performs acquisition bursts following being woken
by SS. This has two effects.
(QT2100 Input - MOSI)
(QT2100 Input - MOSI)
(QT2100 Out - MISO)
(QT2100 Out - MISO)
• Touch detection only occurs following SS-wake pulses, and hence CHANGE can only go
• The QT2100 cannot drift its internal references unless the host sends periodic SS-wake
Host Data Output
Host Data Output
high at that time.
pulses. If the host does not do this, then it should command the QT2100 to recalibrate
when it sets the QT2100 into a different operating mode.
SCLK from Host
SCLK from Host
QT Data Output
QT Data Output
Acquire Bursts
Acquire Bursts
/SS from host
/SS from host
With LPB = 1, a pulse on
follow communications. Pulse width > 22 µs.
LP Mode SPI Operation
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SS Pulse Wake
>22us
3-state
>22us
3-state
No SPI Communication
SS
SPI Operation with LPB = 0
SPI Operation with LPB = 1
with or without communications triggers an acquisition burst to
don't care
don't care
don’t care
don’t care
SPI communications Wake
SPI Communication
command bytes
response bytes
command bytes
response bytes
3-state
3-state
9554CX–AT42–11/11
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don't care
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don’t care