8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
APPLICATION NOTE: The PWM frequency is determined based on the selected LED behavior, the programmed
breathe period, and the programmed min and max duty cycles. For the Direct Mode, the
PWM frequency is calculated based on the programmed Rise and Fall times. If these are
set at 0, then the maximum PWM frequency will be used based on the programmed duty
cycle settings.
5.28 LED Pulse 1 Period Register
Table 5.44 LED Pulse 1 Period Register
ADDR
R/W
REGISTER
B7
B6
B5
B4
B3
B2
B1
B0
DEFAULT
LED Pulse 1
Period
ST_
TRIG
P1_
PER6
P1_
PER5
P1_
PER4
P1_
PER3
P1_
PER2
P1_
PER1
P1_
PER0
84h
R/W
20h
The LED Pulse Period 1 register determines the overall period of a pulse operation as determined by
the LED_CTL registers (see Table 5.43 - setting 01b). Each LSB represents 32ms so that a setting of
14h (20d) would represent a period of 640ms. The total range is from 32ms to 4.06 seconds as shown
in Table 5.45.
APPLICATION NOTE: Due to constraints on the LED Drive PWM operation, any Breathe Period less than 160ms
(05h) may not be achievable. The device will breathe at the minimum period possible as
determined by the period and min / max duty cycle settings.
Bit 7 - ST_TRIG - Determines the start trigger for the LED Pulse behavior.
‘0’ (default) - The LED will Pulse when a touch is detected.
‘1’ - The LED will Pulse when a release is detected.
The Pulse 1 operation is shown in Figure 5.1 when the LED output is configured for non-inverted
polarity and in Figure 5.2 for inverted polarity.
.
Touch Detected or
Release Detected
X pulses after touch or after release
Normal – untouched
operation
Normal – untouched
operation
(100% - Pulse 1 Min Duty Cycle) * Brightness
LED
Brightness
(100% - Pulse 1 Max Duty Cycle) * Brightness
Pulse 1 Period
(P1_PER)
Figure 5.1 Pulse Behavior with Non-Inverted Polarity
SMSC CAP1088
Revision 1.1 (08-05-09)
DATA5S9HEET
SMSC [ SMSC CORPORATION ]
