Datasheet

The TIME and SNS pins are used to configure the Auto-off delay and must always be connected in one of
the ways described in Section 3.11.2.
3.11.2 Auto-off – Predefined Delay
To configure the predefined delay the TIME pin is hard wired to Vss, Vdd or OUT as shown in Table 3-2
and Table 3-3. This provides nominal values of 15 minutes, 60 minutes or infinity (remains on until
toggled off).
A single 1 MΩ resistor (Rm) is connected between the SNS pin and the logic level Vm to provide three
auto-off functions: delay multiplication, delay override and delay retriggering. On power-up the logic level
at Vm is assessed and the delay multiplication factor is set to x1 or x24 accordingly (see Figure 3-6, Table
3-2 and Table 3-3). At the end of each acquisition cycle the logic level of Vm is monitored to see if an
Auto-off delay override is required (see Section 3.11.5).
Setting the delay multiplier to x24 will decrease the key sensitivity. To compensate, it may be necessary to
increase the value of Cs.
Figure 3-6. Predefined Delay
VDD
OUT
VSS
2
1
4
SNS
Rm
Vm
TIME
6
Vt
3
SNSK
Cs
SENSE
ELECTRODE
Rs
Rop
5
VDD
Cby
100 nF
Table 3-2. Predefined Auto-off Delay (Active High Output)
Vt Auto-off Delay (t
o
)
Vss Infinity (remain on until toggled to off)
Vdd 15 minutes
OUT 60 minutes
AT42QT1012
© 2017 Microchip Technology Inc.
Datasheet
DS40001948A-page 14