CAP1028 datasheet(55/71 Pages) SMSC

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8 Channel Capacitive Touch Sensor with 2 LED Drivers

Datasheet

SMSC CAP1028

Revision 1.1 (08-05-09)

DATASHEET

‘0’ - The LED2 output is inverted. A setting of ‘1’ in the LED Output register will cause the output

to be driven to a logic ‘0’ as determined by the LED behavior. Similarly, the duty cycles

corresponding to Pulse and Breathe operations will indicate the amount of time that the LED is

driven to a logic ‘0’ state (corresponding to “active”).

‘1’ - The LED2 output is non-inverted. A setting of ‘1’ in the LED Output register will cause the

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

behavior. Similarly, the duty cycles corresponding to Pulse and Breathe operations will indicate to

the amount of time that the LED is driven to a logic ‘1’ state (corresponding to “inactive”).

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

5.26

LED Output Control Register

The LED Output Control Register controls the output state of the LED pins.

All LEDs that are associated with a Capacitive Touch Sensor channel are automatically enabled and

will be actuated per the LED Behavior.

For those LEDs that are not linked with a Capacitive Touch Sensor channel, then the bit state

determines whether the LED is actuated or not actuated.

The LED Polarity Control register will determine the non actuated state of the LED pins.

Table 5.41 shows the interaction between the polarity controls, output controls and relative brightness.

Note 5.3

For example: when polarity is non-inverted, if min duty cycle is 0, then the LED would be

at logic 1 (off) 0% of the time. It will be at logic 0 (on), 100% of the time (100 - min duty

cycle).

Bit 1 - LED2_DR - Determines whether LED2 output is driven high or low.

Table 5.40 LED Output Control Register

ADDR

R/W

DEFAULT

74h

R/W

LED Output

Control

---

LED2_

LED1_

00h

Table 5.41 LED Polarity Behavior

LED

OUTPUT

CONTROL

POLARITY

MAX DUTY

MIN DUTY

LED

BEHAVIORS

BRIGHTNESS

LED

APPEARANCE

inverted

maximum % of

time that the LED

is on (logic 0)

minimum % of

time that the LED

is on (logic 0)

off

maximum brightness at

minimum duty cycle

on at minimum

duty cycle

inverted

maximum % of

time that the LED

is on (logic 0)

minimum % of

time that the LED

is on (logic 0)

maximum brightness at

max duty cycle. Brightness

ramps from min to max

according to

LED behavior

non-

inverted

maximum % of

time that the LED

is off (logic 1)

minimum % of

time that the LED

is off (logic 1)

off

maximum brightness at 100

- min duty cycle

on at 100 - min

duty cycle

(Note 5.3)

non-

inverted

maximum % of

time that the LED

is off (logic 1)

minimum % of

time that the LED

is off (logic 1)

maximum brightness at 100

- min duty cycle. Brightness

ramps from max to min

according to

LED behavior

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