CAP1128 datasheet(51/75 Pages) MICROCHIP

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DS00001622B-page 51

CAP1128

APPLICATION NOTE: The polarity controls determine the final LED pin drive. A touch on a linked capacitive touch

sensor input is treated in the same way as the LED Output Control bit being set to a logic ‘1’.

APPLICATION NOTE: The LED drive assumes that the LEDs are configured such that if the LED pin is driven to

a logic ‘0’ then the LED will be on and that the CAP1128 LED pin is sinking the LED current.

Conversely, if the LED pin is driven to a logic ‘1’, the LED will be off and there is no current

flow. See Figure 5-1, "System Diagram for CAP1128".

APPLICATION NOTE: This application note applies when the LED polarity is inverted (LEDx_POL = ‘0’). For LED

operation, the duty cycle settings determine the % of time that the LED pin will be driven to

a logic ‘0’ state in. The Max Duty Cycle settings define the maximum % of time that the LED

pin will be driven low (i.e. maximum % of time that the LED is on) while the Min Duty Cycle

settings determine the minimum % of time that the LED pin will be driven low (i.e. minimum

% of time that the LED is on). When there is no touch detected or the LED Output Control

Breathe operations will ramp the duty cycle from the minimum duty cycle to the maximum

duty cycle.

APPLICATION NOTE: This application note applies when the LED polarity is non-inverted (LEDx_POL = ‘1’). For

LED operation, the duty cycle settings determine the % of time that the LED pin will be driven

to a logic ‘1’ state. The Max Duty Cycle settings define the maximum % of time that the LED

pin will be driven high (i.e. maximum % of time that the LED is off) while the Min Duty Cycle

settings determine the minimum % of time that the LED pin will be driven high (i.e. minimum

% of time that the LED is off). When there is no touch detected or the LED Output Control

cycle setting. Breathe operations will ramp the duty cycle from 100 minus the minimum duty

cycle to 100 minus the maximum duty cycle.

APPLICATION NOTE: The LED Mirror controls (see Section 6.30, "LED Mirror Control Register") work with the

polarity controls with respect to LED brightness but will not have a direct effect on the output

pin drive.

Bit 1 - LED2_POL - Determines the polarity of the LED2 output.

• ‘0’ (default) - The LED2 output is inverted. For example, a setting of ‘1’ in the LED Output Control register will

cause the LED pin output to be driven to a logic ‘0’.

• ‘1’ - The LED2 output is non-inverted. For example, a setting of ‘1’ in the LED Output Control register will cause

the LED pin output to be driven to a logic ‘1’ or left in the high-z state as determined by its output type.

Bit 0 - LED1_POL - Determines the polarity of the LED1 output.

6.28

LED Output Control Register

The LED Output Control Register controls the output state of the LED pins that are not linked to sensor inputs.

The LED Polarity Control Register will determine the non actuated state of the LED pins. The actuated LED behavior is

determined by the LED behavior controls (see Section 6.31, "LED Behavior Register").

TABLE 6-47:

LED OUTPUT CONTROL REGISTER

ADDR

R/W

Default

74h

R/W

LED Output

Control

---

LED2_

LED1_

00h

Note:

If an LED is linked to a sensor input in the Sensor Input LED Linking Register (Section 6.26, "Sensor Input

LED Linking Register"), the corresponding bit in the LED Output Control Register is ignored (i.e. a linked

LED cannot be host controlled).

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