LP3958

SNVS423C – JANUARY 2006 – REVISED MARCH 2013

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6. 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(1)

SLOPE

5

FADE execution time:

0 = 1.3s (full scale)

1 = 0.65s (full scale)

FADE_SEL

4

FADE selection:

0 = FADE controls MAIN

1 = FADE controls SUB

EN_FADE

3

FADE enable

0 = FADE disabled

1 = FADE enabled

DISPL

2

Display mode:

0 = MAIN and SUB individual control

1 = MAIN and SUB controlled with MAIN DAC

EN_MAIN

1

MAIN enable:

0 = disable

1 = enable

EN_SUB

0

SUB enable:

0 = disable

1 = enable

(1)

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]

Driver current,

SUB CURRENT [7:0]

mA (typical)

0000 0000

0

0000 0001

0.1

0000 0010

0.2

0000 0011

0.3

…

…

…

…

1111 1101

25.3

1111 1110

25.4

1111 1111

25.5

Backlight Driver Electrical Characteristics

Symbol

Parameter

Test Conditions

Min

Typ

Max

Unit

IMAX

Maximum Sink Current

25.5

30

mA

ILEAKAGE

Leakage Current

VSUB, MAIN =18V

0.03

1

µA

IMAIN

MAIN Current tolerance

IMAIN and ISUB set to 12.8mA (80H)

11.1

12.8

14.1

mA

ISUB

SUB Current tolerance

MatchMAIN-

Sink Current Matching Error(1)

ISINK=12.8mA, DISPL=1

0.2

%

SUB

MatchMAIN-

Sink Current Matching Error

ISINK=12.8mA, DISPL=0

5

%

SUB

VSAT

95% Saturation Voltage

ISINK=25mA

400

600

mV

800

(1)

Matching is the maximum difference from the average.

18

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