LP3958TL datasheet(16/28 Pages) NSC

16 / 28 page

Backlight Drivers (Continued)

FADE IN / FADE OUT

LP3958 has an automatic fade in and out for main and sub

backlight. The fade function is enabled with EN_FADE bit.

The slope of the fade curve is set by the SLOPE bit. Fade

control for main and sub display is set by FADE_SEL bit.

Recommended fading sequence:

ASSUMPTION: Current WLED value in register

Set SLOPE

Set FADE_SEL

Set EN_FADE = 1

Set target WLED value

Fading will be done either within 0.65s or 1.3s based on

SLOPE selection

Fading times apply to full scale change i.e. from 0 to 100% or

vice versa. If the current change does not correspond to full

scale change, the time will be respectively shorter. See

WLED Dimming diagrams for typical fade times.

WLED CONTROL REGISTER (03H)

Name

Bit

Description

SLOPE

FADE execution time:

0 = 1.3s (full scale)

1 = 0.65s (full scale)

FADE_SEL

FADE selection:

0 = FADE controls MAIN

1 = FADE controls SUB

EN_FADE

FADE enable

0 = FADE disabled

1 = FADE enabled

DISPL

Display mode:

0 = MAIN and SUB individual control

1 = MAIN and SUB controlled with

MAIN DAC

EN_MAIN

MAIN enable:

0 = disable

1 = enable

EN_SUB

SUB enable:

0 = disable

1 = enable

Note: if DISPL=1 and FADE_SEL=0 then FADE effects MAIN and SUB

Adjustment is made with 04H (main current) and with 05H

(sub current) registers:

MAIN CURRENT [7:0]

SUB CURRENT [7:0]

Driver current,

mA (typical)

0000 0000

0000 0001

0.1

0000 0010

0.2

0000 0011

0.3

……

1111 1101

25.3

1111 1110

25.4

1111 1111

25.5

LP3958TL Datasheet(PDF) 16 Page - National Semiconductor (TI)

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