Datasheet

Table 3-3. Predefined Auto-off Delay (Active Low Output)
Vt Auto-off Delay (t
o
)
Vss 15 minutes
Vdd Infinity (remain on until toggled to off)
OUT 60 minutes
Table 3-4. Auto-off Delay Multiplier
Vm Auto-off Delay Multiplier
Vss t
o
× 1
Vdd t
o
× 24
3.11.3 Auto-off – User-programmed Delay
If a user-programmed delay is required, a RC network (resistor and capacitor) can be used to set the
auto-off delay (see Table 3-5 and Figure 3-7). The delay time is dependent on the RC time constant (Rt ×
Ct), the output polarity and the supply voltage. Section 3.11.4 gives full details of how to configure the
QT1012 to have auto-off delay times ranging from minutes to hours.
Figure 3-7. Programmable Delay
VDD
OUT
VSS
2
1
4
SNS
Rm
Vm
TIME
6
3
SNSK
Cs
SENSE
ELECTRODE
Rs
Rop
5
VDD
Cby
100 nF
Rop
Cs
3.11.4 Configuring the User-programmed Auto-off Delay
The QT1012 can be configured to give auto-off delays ranging from minutes to hours by means of a
simple RC network and the delay multiplier input.
With the delay multiplier set at x1 the auto-off delay is calculated as follows:
Delay value = integer value of
Rt × Ct
�
x 15 seconds
AT42QT1012
© 2017 Microchip Technology Inc.
Datasheet
DS40001948A-page 15