3 Channel Capacitive Touch Sensor with 3 LED Drivers
Datasheet
Table 5.39 STBY_CY_TIME Bit Decode
STBY_CY_TIME[1:0]
1
0
OVERALL CYCLE TIME
0
0
1
1
0
1
0
1
35ms
70ms (default)
105ms
140ms
APPLICATION NOTE: The programmed cycle time is only maintained if the total averaging time for all samples is
less than the programmed cycle. The STBY_AVG[2:0] bits will take priority so that if more
samples are required than would normally be allowed during the cycle time, the cycle time
will be extended as necessary to accommodate the number of samples to be measured.
5.22
Standby Sensitivity Register
Table 5.40 Standby Sensitivity Register
ADDR
R/W
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
Standby
Sensitivity
42h
-
-
-
-
-
STBY_SENSE[2:0]
02h
The Standby Sensitivity register controls the sensitivity for sensor inputs that are active in Standby.
Bits 2 - 0 - STBY_SENSE[2:0] - Controls the sensitivity for sensor inputs that are active in Standby.
The sensitivity settings act to scale the relative delta count value higher or lower based on the system
parameters. A setting of 000b is the most sensitive while a setting of 111b is the least sensitive. At the
more sensitive settings, touches are detected for a smaller delta C corresponding to a “lighter” touch.
These settings are more sensitive to noise however and a noisy environment may flag more false
touches than higher sensitivity levels.
APPLICATION NOTE: A value of 128x is the most sensitive setting available. At the most sensitivity settings, the
MSB of the Delta Count register represents 64 out of ~25,000 which corresponds to a touch
of approximately 0.25% of the base capacitance (or a ΔC of 25fF from a 10pF base
capacitance). Conversely a value of 1x is the least sensitive setting available. At these
settings, the MSB of the Delta Count register corresponds to a delta count of 8192 counts
out of ~25,000 which corresponds to a touch of approximately 33% of the base capacitance
(or a ΔC of 3.33pF from a 10pF base capacitance).
Table 5.41 STBY_SENSE Bit Decode
STBY_SENSE[2:0]
2
1
0
SENSITIVITY MULTIPLIER
0
0
0
0
0
1
128x (most sensitive)
64x
Revision 1.32 (01-05-12)
SMSC CAP1133
DATA4S6HEET
SMSC [ SMSC CORPORATION ]
