SC657ULTRT Semtech, SC657ULTRT Datasheet - Page 20

• Manufacturer Part Number: SC657ULTRT
• Description: Backlight Driver For 5 LEDs With SemPulseTM Interface
• Manufacturer: Semtech

Register and Bit Definitions (continued)
Main Fade Control (04h)
This register sets the fade status and rate for the main
backlight group.
Bits [D5:D2]
These bits are unused and are always zeros, so the
maximum pulse count for this register is 3.
MFADE1, MFADE0[D1:D0]
These bits are used to enable and set the rise/fall rate
between two backlight currents as follows in Table 7.
The number of steps used to change the backlight current
will be equal to the change in binary count of bits
MBL[4:0].
When a new backlight current is set, the backlight current
will change from its current value to a new value set by
bits MBL[4:0] at the rate determined by MFADE and
MFADE0 bits. The total fade time is determined by the
number of steps between old and new backlight values,
in Table 4, multiplied by the rate of fade in ms/step.
Backlight Grouping Configuration (05h)
This register assigns the LEDs to the back light bank
configurations.
Bits [D5:D3]
These bits are unused and are always zeros, so the
maximum pulse count for this register is 7.
MFADE1
0
0


Table 7 — Main Display Fade Control Bits
MFADE0
0

0

Fade Feature Rise�Fall Rate
(ms�step)
OFF
6
32
8
MB2, MB1 and MB0 [D2:D0]
These bits are used to set the number of LED drivers dedi-
cated to each backlight group. This allows the device to
drive up to three different sets of LEDs with different
current settings. Note that any driver assigned to any LED
group can still be disabled independently if not needed.
The code set by these bits determines how the LED drivers
are assigned among the three LED groups according to
the assignments listed in Table 8. Default state for each of
these three bits is “0” (all LEDs assigned to main display).
MB2 MB1 MB0
0
0
0
0



Table 8 — Backlight Grouping Configuration
0
0


0
0

X
0

0

0

Display
Drivers
BL-BL2,
BL-BL5
BL-BL3
BL-BL2
BL-BL3
BL-BL4
BL-BL5
Main
LED
BL5
Display
Drivers
BL4-BL5
BL3-BL4
BL4-BL5
Sub
LED
BL3
BL5
SC657
Display
Drivers
Third
LED
BL5
BL4
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