LP3954 Datasheet, PDF (28/60 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

LP3954
SNVS340D – JUNE 2005 – REVISED MARCH 2013
ADJUSTMENT
WLED1-4[7:0]
WLED5-6[7:0]
0000 0000
0000 0001
0000 0010
0000 0011
…
…
1111 1101
1111 1110
1111 1111
Driver Current,
mA (typical)
0
0.1
0.2
0.3
…
…
25.3
25.4
25.5
30
25^oC
25
20
-40^oC
85^oC
15
10
5
0
0 0.05 0.10 0.15 0.20 0.25 0.30
WLED OUTPUT VOLTAGE (V)
Figure 28. WLED Output Current vs. Voltage
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FADE IN / FADE OUT
LP3954 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.
EN_FADE
SLOPE
FADE_SEL
0
Automatic fade disabled
1
Automatic fade enabled
0
Fade execution time 1.3s
1
Fade execution time 0.65s
0
Fade controls WLED1-4
1
Fade controls WLED5-6
Recommended fading sequence:
1. ASSUMPTION: Current WLED value in register
2. Set SLOPE
3. Set FADE_SEL
4. Set EN_FADE = 1
5. Set target WLED value
6. Fading will be done either within 0.5s or 1s based on Slope selection
28
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