LP3954 Datasheet, PDF (25/56 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

Backlight Drivers
LP3954 has 2 independent backlight drivers. Both drivers are
regulated constant current sinks. LED current for both LED
banks (WLED1…4 and WLED5…6) are controlled by 8-bit
current mode DACs with 0.1 mA step.
WLED1…4 and WLED5…6 can be also controlled with one
DAC for better matching allowing the use of larger displays
having up to 6 white LEDs in parallel.
Display configuration is controlled with DISPL bit as shown
below.
DISPL
0
1
Configuration
Main display up
to 4 LEDs
Sub display up
to 2 LEDs
Large display
up to 6 LEDs
Matching
Good btw
WLED1…4
Good btw
WLED5…6
Good btw
WLED 1…6
Display backlight enables
EN_W1-4
1 WLED1-4 enabled
0 WLED1-4 disabled
EN_W5-6
1 WLED5-6 enabled
0 WLED5-6 disabled
20132235
Main display up to 4 LEDs (WLED1…4)
20132236
Sub display driver up to 2 LEDs (WLED5…6)
Main display up to 6 LEDs (WLED1…6) (DISPL=1)
20132237
BACKLIGHT DRIVER ELECTRICAL CHARACTERISTICS
Symbol
I_MAX
I_Leakage
I_WLED1
Parameter
Maximum Sink Current
Leakage Current
WLED1 Current tolerance
I_Match1-4
I_Match5-6
I_Match1-6
Sink Current Matching
Sink Current Matching
Sink Current Matching
Note: Matching is the maximum difference from the average.
Conditions
V_FB =5V
I_WLED1 set to 12.8mA (80H)
I_SINK=13mA, Between WLED1…4
I_SINK=13mA, Between WLED5…6
I_SINK=13mA, Between WLED1…6
Min Typical
21.3 25.5
0.03
10.52 12.8
-18
0.2
0.2
0.3
Max
29.4
1
14.78
+16
Units
mA
µA
mA
%
%
%
%
25
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