8 Channel Capacitive Touch Sensor with 8 LED Drivers
Datasheet
5.32 LED Duty Cycle Registers
Table 5.50 LED Duty Cycle Registers
B7 B6 B5 B4 B3
ADDR
R/W
REGISTER
B2
B1
B0
DEFAULT
LED Pulse 1
Duty Cycle
90h
R/W
P1_MAX_DUTY[3:0]
P2_MAX_DUTY[3:0]
BR_MAX_DUTY[3:0]
DR_MAX_DUTY[3:0]
P1_MIN_DUTY[3:0]
P2_MIN_DUTY[3:0]
BR_MIN_DUTY[3:0]
DR_MIN_DUTY[3:0]
F0h
LED Pulse 2
Duty Cycle
91h
92h
93h
R/W
R/W
R/W
F0h
F0h
F0h
LED Breathe
Duty Cycle
Direct Duty
Cycle
The LED Duty Cycle registers determine the minimum and maximum duty cycle settings used for the
LED for each LED behavior. These settings affect the brightness of the LED when it is fully off and
fully on.
The LED driver duty cycle will ramp up from the minimum duty cycle (see Section 5.32) to the
maximum duty cycle and back down again.
APPLICATION NOTE: Changes to the Duty Cycle settings will be applied immediately. When the respective register
is written, the LED output will be reset to the minimum (or maximum) setting and restarted
at the updated settings.
APPLICATION NOTE: Upon power on reset (or upon release of the RESET pin), the first breath will breathe from
100% (or 0% duty cycle as determined by the polarity registers) to the programmed minimum
(or maximum as determined by the polarity registers) and then proceed normally.
APPLICATION NOTE: If the min duty cycle and the max duty cycle are set to the same % then the minimum duty
cycle will automatically be changed to the next lower setting. For example, if the maximum
duty cycle were set at 1100b (35%) and the minimum duty cycle were set at 1101b (35%),
the device will automatically use the minimum value at 1100b (25%).
Bits 7 - 4 - X_MAX_DUTY[3:0] - Determines the maximum PWM duty cycle for the LED drivers as
shown in Table 5.51
Bits 3 - 0 - X_MIN_DUTY[3:0] - Determines the minimum PWM duty cycle for the LED drivers as
shown in Table 5.51.
Table 5.51 LED Duty Cycle Decode
X_MAX/MIN_DUTY [3:0]
3
2
1
0
MAXIMUM DUTY CYCLE
MINIMUM DUTY CYCLE
0
0
0
0
0
0
0
0
0
1
0
0
1
1
0
0
1
0
1
0
1%
2%
3%
4%
5%
0%
1%
2%
3%
4%
SMSC CAP1088
Revision 1.1 (08-05-09)
DATA6S3HEET
SMSC [ SMSC CORPORATION ]
