ON

ON

ON

FRAME

50 Ps/20 kHz

RED

GREEN

BLUE

RGB

Ð

RED

25%

GREEN

25%

BLUE

50%

ON

ON

ON

FRAME

50 és/20 kHz

RED

GREEN

BLUE

LP5526

SNVS431C – FEBRUARY 2006 – REVISED JULY 2009

www.ti.com

Overlapping Mode

In overlapping mode the brightness is controlled using PWM duty cycle based control method as the following

figure shows.

Figure 5. Overlapping Mode

Since RGB outputs are on simultaneously, the maximum load peak current is:

(1)

Non-Overlapping Mode

The timing diagram shows the split R, G and B and brightness control effect to split parts. Full brightness is used

in the diagram. If for example ½ 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.

Figure 6. Non-Overlapping Mode

The non-overlapping mode has 16 programmed colors (different R, G and B ratio -> different color). Since the R,

G and B are split into non-overlapping slots the output current through the RGB LED can be calculated with

following equation:

(2)

where

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

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

2. LED ON/OFF CONTROL WITH RGB CONTROL REGISTER

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.

Switch Mode / Constant Current Mode

Each RGB LED output can be set to act as a switch or a constant current sink. Selection of mode is done with

the CC_SW bit in the Control Register. If bit is set high, then the switch mode is selected. Default is switch mode.

14

Submit Documentation Feedback

Copyright © 2006–2009, Texas Instruments Incorporated

Product Folder Links: LP5526