Datasheet

8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
Revision 1.32 (01-05-12) 64 SMSC CAP1188
DATASHEET
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 C 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 C of 3.33pF from a 10pF base capacitance).
5.23 Standby Threshold Register
The Standby Threshold register stores the delta threshold that is used to determine if a touch has been
detected. When a touch occurs, the input signal of the corresponding sensor pad changes due to the
capacitance associated with a touch. If the sensor input change exceeds the threshold settings, a
touch is detected.
Table 5.41 STBY_SENSE Bit Decode
STBY_SENSE[2:0]
SENSITIVITY MULTIPLIER2 1 0
0 0 0 128x (most sensitive)
0 0 1 64x
0 1 0 32x (default)
0 1 1 16x
1 0 0 8x
1 0 1 4x
1 1 0 2x
1 1 1 1x - (least sensitive)
Table 5.42 Standby Threshold Register
ADDR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAULT
43h R/W
Standby
Threshold
- 64 32 16 8 4 2 1 40h