E102 Atmel, E102 Datasheet - Page 9

• Manufacturer Part Number: E102
• Description: KIT EVAL/DEV USING QT102-ISG
• Manufacturer: Atmel
• Series: Quantum, QTouch™r

Specifications of E102

• Sensor Type: Touch, Capacitive
• Sensing Range: 1 Button/Key
• Interface: Logic Level
• Voltage - Supply: 3V
• Embedded: No
• Utilized Ic / Part: QT102
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Sensitivity: -

To ensure the pulse is detected it must be present for a time
greater than the burst length as shown in Table 3.6.
While Vm is held in the override state the QT102 inhibits
bursts and waits for Vm to return to its original state. When
Vm returns to its original state the QT102 performs a sensor
recalibration before continuing in its current output state.
Figure 3.9 shows override pulses being applied to a QT102
with delay multiplier set to x1.
lQ
Pulse Duration
tp > burst time + 10ms
(typical value 25ms)
tp > burst time + 50ms
(typical value 65ms)
Figure 3.8 Override Pulse (Delay Multiplier x24)
Figure 3.7 Override Pulse (Delay Multiplier x1)
VDD
VDD
VSS
VSS
Vm
Vm
ELECTRODE
Tp
ELECTRODE
Tp
Table 3.6 Time Delay Pulse
SENSE
SENSE
RS
RS
CS
CS
Rm
Rm
4
4
3
3
SNS
SNS
SNSK
SNSK
Action
Retrigger (reload auto-off delay
counter)
Switch output to off state and
inhibit further touch detection until
Vm returns to original state
VDD
VDD
VDD
VDD
VSS
VSS
5
5
2
2
TIME
TIME
OUT
OUT
1
1
6
6
Rop
Rop
9
3.5.5 Configuring the User-programmed Auto-off
As described in Section 3.5.3, page 8, the QT102 can be
configured to give auto-off delays ranging from minutes to
hours by means of a simple CR 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 x Ct x 15 seconds.
And Rt x Ct = Delay (in seconds) x K
Note: Rt is in k , Ct is in nF.
To ensure correct operation it is recommended that the value
of Rt x Ct is between 4 and 240.
Values outside this range may be interpreted as the hard
wired options TIME linked to OUT and TIME linked to ‘off’
respectively, causing the QT102 to use the relevant
predefined auto-off delays.
The charts in Figures 3.10 and 3.11 show typical values of K
versus supply voltage for a QT102 with active high or active
low output.
Example using the formula to calculate Rt and Ct
Requirements:
Proceed as follows:
As an alternative to calculation, Figures 3.12 and 3.13 show
charts of typical curves of auto-off delay against resistor and
capacitor values for active high and active low outputs at
various values of VDD (delay multiplier = x1).
•
•
•
1. Calculate Auto-off delay in seconds 45 x 60 = 2700
2. Obtain K from Figure 3.10, K= 42
3. Calculate Rt x Ct = 2700 x 42 = 7560
4. Decide on a value for Rt or Ct (e.g.Ct = 47nF)
5. Calculate Rt = 7560 = 160k
SNSK
OUT
P - override (reload auto off delay)
O - switch output off (t
C - sensor recalibration
Vm
Delay
K
Active high output (Vop connected to VSS)
Auto-off delay 45 minutes
VDD = 3.5V
Bursts
Figure 3.9 Overriding Auto Off
P
C
off
15
47
burst time + 50ms)
P
C
15
K
P
C
QT102_2R3.05_1007
t
off
O
C