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ADP8863

Rev. 0 | Page 15 of 48

1.00

The Cubic 10 and Cubic 11 laws also use the square law LED

currents derived from Equation 3; however, the time between

each step is varied to produce a steeper slope at higher currents

and a shallower slope at lower currents (see Figure 29).

0.75

0.50

0.25

UNIT FADE TIME

LINEAR

SQUARE

CUBIC 11

CUBIC 10

Figure 29. Comparison of the Dimming Transfers Laws

Each LED can be enabled independently and has its own

current level, but all LEDs share the same fade in rates, fade out

rates, and fade law.

INDEPENDENT SINK CONTROL

Each of the seven LEDs can be configured (in Register 0x05) to

operate as either part of the backlight or to operate as an indepen-

dent sink current (ISC). Each ISC can be enabled independently

and has its own current level. All ISCs share the same fade in

rates, fade out rates, and fade law.

The ISCs have additional timers to facilitate blinking functions.

A shared on timer (SCON) in conjunction with the off timer of

each ISC (SC1OFF, SC2OFF, SC3OFF, SC4OFF, SC5OFF, SC6OFF,

and SC7OFF) allows the LED current sinks to be configured in

various blinking modes. The on timer can be set to one of four

different settings: 0.2 sec, 0.6 sec, 0.8 sec, or 1.2 sec. The off

timers have four different settings: disabled, 0.6 sec, 1.2 sec, and

1.8 sec. Blink mode is activated by setting the off timers to any

setting other than disabled.

Program all fade, on, and off timers before enabling any of the

LED current sinks. If ISCx is on during a blink cycle and

SCx_EN is cleared, the LED turns off (or fades to off if fade out

is enabled). If ISCx is off during a blink cycle and SCx_EN is

cleared, it stays off.

MAX

SCx_EN

FADE-IN

FADE-OUT FADE-IN

FADE-OUT

ON TIME

SET BY USER

ISCx

OFF

TIME

OFF

TIME

Figure 30. Independent Sink Blink Mode with Fading

RGB COLOR GENERATION

The ADP8863 is easily programmed to generate any color with

an RGB LED. To configure this feature, connect each LED in a

standard RGB diode to a separate driver on the ADP8863.

Because each channel can be programmed for a different

current level, setting the currents for all three LEDs generates

the desired color. To set the current levels, use a simple RGB

color selector (see Figure 31).

Figure 31. Standard RGB Color Generator

The example in Figure 31 shows a color of green, which is gener-

ated with a red content of 18 (out of 255), a green content of

190, and a blue content of 96. All numbers are out of a maximum

of 255. Thus, the percentage of red is 7.1%, the percentage of

green is 74.5%, and the percentage of blue is 37.6%. To generate

the color with the ADP8863, scale this value to each of the current

drivers.

AUTOMATED RGB COLOR FADES

The ADP8863 is easily programmed to cycle through RGB

generated colors. This can be either a repeating or a random

pattern of one color fading into the other. To execute this cycle

autonomously, set up the RGB LEDs as described in the RGB

Color Generation section and program the on, off, fading times,

and current intensities. Adjusting the fading time in particular

can create any pattern from a fast, striking effect to a soothing

slow color change.

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