CAP1214 datasheet(82/107 Pages) MICROCHIP

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Multiple Channel Capacitive Touch Sensor and LED Driver

Datasheet

Revision 1.0 (08-30-10)

SMSC CAP1214

DATASHEET

6.46.2

LED Output Control 2

Bit 2 - LED11_DR - Determines whether LED11 is driven high or low. This LED cannot be linked to a

Capacitive Touch Sensor.

‘0’ (default) - The LED11 output is driven at the minimum duty cycle or is not actuated

‘1’ - The LED11 output is high-Z or driven at the maximum duty cycle or is actuated.

Bit 1 - LED10_DR - Determines whether LED10 is driven high or low. If this LED is linked to the Group

of sensors, LED9 is automatically linked to the Group if sensors.

Bit 0 - LED9_DR - Determines whether LED9 is driven high or low.

6.47

LED Polarity Registers

The LED Polarity Registers control the logical polarity of the LED outputs. When these bits are set or

cleared, the corresponding LED Mirror controls are also set or cleared (unless the BLK_POL_MIR bit

is set - see Section 6.33). Table 6.68, "LED Polarity Behavior" shows the interaction between the

polarity controls, output controls, and relative brightness.

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

Sensor 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’, the LED will be on and the CAP1214 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 CAP1214".

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 an inverted system. 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 register bit is at a logic ‘0’, the LED output will be driven at the minimum

duty cycle setting. 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 in a non-inverted system. 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 register bit is at a logic ‘0’, the LED output will be driven

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

from 100 minus the minimum duty cycle to 100 minus the maximum duty cycle.

Table 6.67 LED Polarity Registers

ADDR

R/W

DEFAULT

75h

R/W

LED Polarity

LED8_

POL

LED7_

POL

LED6_

POL

LED5_

POL

LED4_

POL

LED3_

POL

LED2_

POL

LED1_

POL

00h

76h

R/W

LED Polarity

LED11_

POL

LED10_

POL

LED9_

POL

00h

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