Datasheet

8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
SMSC CAP1188 73 Revision 1.32 (01-05-12)
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 behavior
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.
5.32 LED Pulse 1 Period Register
The LED Pulse Period 1 register determines the overall period of a pulse operation as determined by
the LED_CTL registers (see Table 5.52 - setting 01b). The LSB represents 32ms so that a setting of
18h (24d) would represent a period of 768ms (24 x 32ms = 768ms). The total range is from 32ms to
4.064 seconds as shown in Table 5.54 with the default being 1024ms.
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 or the drive bit is set.
‘1’ - The LED will Pulse when a release is detected or the drive bit is cleared.
The Pulse 1 operation is shown in Figure 5.1 when the LED output is configured for non-inverted
polarity (LEDx_POL = 1) and in Figure 5.2 for inverted polarity (LEDx_POL = 0).
.
Table 5.53 LED Pulse 1 Period Register
ADDR R/W REGISTER B7 B6 B5 B4 B3 B2 B1 B0 DEFAULT
84h R/W
LED Pulse
1 Period
ST_
TRIG
P1_
PER6
P1_
PER5
P1_
PER4
P1_
PER3
P1_
PER2
P1_
PER1
P1_
PER0
20h
Figure 5.1 Pulse 1 Behavior with Non-Inverted Polarity
Normal – untouched
operation
Normal – untouched
operation
Touch Detected or
Release Detected
(100% - Pulse 1 Max Duty Cycle) * Brightness
X pulses after touch or after release
Pulse 1 Period
(P1_PER)
(100% - Pulse 1 Min Duty Cycle) * Brightness
LED
Brightness