AT42QT1012_10 ATMEL [ATMEL Corporation], AT42QT1012_10 Datasheet - Page 16

• Manufacturer Part Number: AT42QT1012_10
• Description: One-channel Toggle-mode Touch Sensor IC with Power Management Functions
• Manufacturer: ATMEL [ATMEL Corporation]

16
AT42QT1012
Example using a chart to calculate Rt and Ct
Requirements:
Figure 3-10. Auto-off Delay, Active Low Output
• Active low output (Vop connected to VSS)
• Auto-off delay 25 minutes
• VDD = 4V
1. Calculate Auto-off delay in seconds 25 x 60 = 1500.
2. Find
3. This shows the following suitable Ct / Rt combinations:
4000
3500
3000
2500
2000
1500
1000
3500
3000
2500
2000
1500
1000
500
500
0
0
– 100 nF / 20 k
– 47 nF / 40 k
– 22 nF / 90 k
– 10 nF / 190 k
Note: the Auto-off delay times shown are nominal and will vary from chip to chip and with
capacitor and resistor tolerance.
0
0
Ct = 100nF
Ct = 100nF
1500
------------ -
50
50
1
Vm = Vss (delay multiplier = x1)
= 1500 on the 4V chart in
Timing Resistor Rt (K ohms)
Timing Resistor Rt (K ohms)
5V Active Low
3V Active Low
100
100
Ct = 47nF
Ct = 47nF
150
150
200
200
Ct = 22nF
Ct = 10nF
Ct = 22nF
Ct = 10nF
Figure
250
250
4000
3500
3000
2500
2000
1500
1000
3500
3000
2500
2000
1500
1000
3-10.
500
500
0
0
0
0
Ct = 100nF
Ct = 100nF
50
50
Ct = 47nF
Timing Resistor Rt (K ohms)
Timing Resistor Rt (K ohms)
4V Active Low
2V Active Low
100
100
Ct = 47nF
150
150
9543D–AT42–08/10
200
200
Ct = 22nF
Ct = 22nF
Ct = 10nF
Ct = 10nF
250
250