CAP1028 datasheet(62/71 Pages) SMSC

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8 Channel Capacitive Touch Sensor with 2 LED Drivers

Datasheet

Revision 1.1 (08-05-09)

SMSC CAP1028

DATASHEET

5.32

LED Duty Cycle Registers

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 5.50 LED Duty Cycle Registers

ADDR

R/W

DEFAULT

90h

R/W

LED Pulse 1

Duty Cycle

P1_MAX_DUTY[3:0]

P1_MIN_DUTY[3:0]

F0h

91h

R/W

LED Pulse 2

Duty Cycle

P2_MAX_DUTY[3:0]

P2_MIN_DUTY[3:0]

F0h

92h

R/W

LED Breathe

Duty Cycle

BR_MAX_DUTY[3:0]

BR_MIN_DUTY[3:0]

F0h

93h

R/W

Direct Duty

Cycle

DR_MAX_DUTY[3:0]

DR_MIN_DUTY[3:0]

F0h

Table 5.51 LED Duty Cycle Decode

X_MAX/MIN_DUTY [3:0]

MAXIMUM DUTY CYCLE

MINIMUM DUTY CYCLE

CAP1028 Datasheet(PDF) 62 Page - SMSC Corporation

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