LP5520 datasheet(10/45 Pages) TI2

10 / 45 page

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TEMPERATURE

4000

3500

3000

2500

2000

1500

1000

500

Red

Blue

Green

4000

3500

2500

2000

3000

1500

1000

500

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

700

620

600

580

560

540

520

500

480

470

Target for white

light

Green

Blue

Red

460

490

380

0.1

0.3

0.4

0.5

0.6

0.7

0.8

0.2

VDDIO

Power ON

Power OFF

VDDD and VDDA

LP5520

SNVS440B – MAY 2007 – REVISED MARCH 2016

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Product Folder Links: LP5520

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Feature Description (continued)

Figure 9. Power-On Signal Timing

7.3.2 RGB Driver Functionality

7.3.2.1 White Balance Control

The LP5520 is designed to provide spectrally rich white light using a three-color RGB LED. White light is

obtained when the red, green, and blue LED intensities are in proper balance. The LED intensities change

independently with temperature. For maintaining the purity of the white color and the targeted total intensity,

precise temperature dependent intensity control for each LED is required. The color coordinates in this document

refer to the CIE 1931 color graph (x,y system).

Figure 10. CIE 1931 Color Graph

Figure 11 shows a typical RGB LED intensity behavior on a 12-bit scale (0 to 4095) at constant 20-mA LED

currents. Figure 12 shows the typical color coordinate change for an uncompensated RGB LED. Figure 13 shows

the corresponding PWM values for achieving constant intensity white light across the temperature range. The

PWM values have been saturated at 104°C to avoid overheating the LED and to better utilize the PWM range.

The white balance is not maintained above 104°C in this case.

Figure 11. LED Intensity vs Temperature

LP5520 Datasheet(PDF) 10 Page - Texas Instruments

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