LP5526 datasheet(13/33 Pages) NSC

13 / 33 page

Functionality of Color LED Outputs (RLED, GLED, BLED) (Continued)

Overlapping Mode

In overlapping mode the brightness is controlled using PWM

duty cycle based control method as the following figure

shows.

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Overlapping Mode

Since RGB outputs are on simuneltaneously, the maximum

load peak current is:

MAX = I(RLED)MAX + I(GLED)MAX + I(BLED)MAX

Non-Overlapping Mode

The timing diagram shows the splitted R, G and B and

brightness control effect to splitted parts. Full brightness is

used in the diagram. If for example 1⁄2 brightness is used, the

frame is still 50µs, but all LED outputs’ ON time is 50%

shorter and at the last 25µs all LED outputs are OFF.

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Non-Overlapping Mode

The non-overlapping mode has 16 programmed colors (dif-

ferent R, G and B ratio -> different color). Since the R, G and

B are split in to non-overlapping slots the output current

through the RGB LED can be calculated with following equa-

tion:

AVG=(CRxIR+CGxIG+CBxIB)xB

where

C = Color [%] (see table of color control)

B = Brightness [%] (see table of brightness control)

2. LED ON/OFF CONTROL WITH RGB CONTROL

Each LED output can be set ON by writing the corresponding

bit high in the Control register (00H). RSW controls RLED,

GSW controls GLED and BSW controls BLED output. Note

that EN_RGB bit must be high and RGB_PWM bit low. In this

mode, the RGB register (01H) does not have any effect.

CC_SW bit in Control register defines the LED output mode.

LP5526 数据表(PDF) 13 Page - National Semiconductor (TI)