LP8556 Datasheet, PDF (40/52 Pages) Texas Instruments – High-Efficiency LED Backlight Driver for Tablets

LP8556
SNVS871B – JULY 2012 – REVISED SEPTEMBER 2012
CFG4
Address A4h
CFG4 register
7
6
5
PWM_TO_I_THRESHOLD[3:0]
Name
Bit
PWM_TO_I_
7:4
_THRESHOLD
Access
R/W
RESERVED
3
R/W
STEADY_DITHER
2
R/W
DITHER
1:0
R/W
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4
3
2
RESERVED
STEADY_
_DITHER
1
0
DITHER[1:0]
Description
Select switch point between PWM and pure current dimming
0000 = current dimming across entire range
0001 = switch point at 10% of the maximum LED current.
0010 = switch point at 12.5% of the maximum LED current.
0011 = switch point at 15% of the maximum LED current.
0100 = switch point at 17.5% of the maximum LED current.
0101 = switch point at 20% of the maximum LED current.
0110 = switch point at 22.5% of the maximum LED current.
0111 = switch point at 25% of the maximum LED current. This is a
recommended selection.
1000 = switch point at 33.33% of the maximum LED current.
1001 = switch point at 41.67% of the maximum LED current.
1010 = switch point at 50% of the maximum LED current.
1011 to 1111 = PWM dimming across entire range
Dither function method select:
0 = Dither only on transitions
1 = Dither at all times
Dither function control
00 = Dithering disabled
01 = 1-bit dithering
10 = 2-bit dithering
11 = 3-bit dithering
CFG5
Address A5h
CFG5 register
7
PWM_DIRECT
Name
PWM_DIRECT
PS_MODE
6
5
4
3
2
1
0
PS_MODE[2:0]
PWM_FREQ[3:0]
Bit
Access
Description
7
R/W
Intended for certain test mode purposes. When enabled, the entire pipeline is
bypassed and PWM output is connected with PWM input.
6:4
R/W
Select PWM output phase configuration:
000 = 6-phase, 6 drivers (0°, 60°, 120°, 180°, 240°, 320°)
001 = 5-phase, 5 drivers (0°, 72°, 144°, 216°, 288°, OFF)
010 = 4-phase, 4 drivers (0°, 90°, 180°, 270°, OFF, OFF)
011 = 3-phase, 3 drivers (0°, 120°, 240°, OFF, OFF, OFF)
100 = 2-phase, 2 drivers (0°, 180°, OFF, OFF, OFF, OFF)
101 = 3-phase, 6 drivers (0°, 0°, 120°, 120°, 240°, 240°)
110 = 2-phase, 6 drivers (0°, 0°, 0°, 180°, 180°, 180°)
111 = 1-phase, 6 drivers (0°, 0°, 0°, 0°, 0°, 0°)
40
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