SC643 Datasheet, PDF (24/26 Pages) Semtech Corporation – Light Management Unit with 4 LDOs and SemPulse®Interface

SC643
Register Map (continued)
SFADE1 and SFADE0 [D5:D4]
These bits are used to set the rise/fall rate between two
backlight currents for the sub display as show in Table 11.
For the fade feature to be active, the SFADE bit must be
set. The number of steps required to change the backlight
current will be equal to the change in binary count of bits
SBL4 through SBL0.
Bank Selection Register (0Ah)
This register contains the bits that determine which LED
drivers are assigned to the main display and which are
part of the sub display bank.
Bits [D5:D3]
These bits are unused and are always zeroes.
Table 11 — Sub Display Fade Control Bits
SFADE1
SFADE0
Fade Feature Rise/
Fall Rate (ms/step)
0
0
32
0
1
24
1
0
16
1
1
8
SFADE [D3]
This bit is used to enable or disable the fade feature. When
SFADE is enabled and a new main backlight current is set,
the current will change from its existing setting to the new
setting written in SBL[4:0] at the rate determined by
SFADE1 and SFADE0 (in ms/step). A new setting cannot
be written during an ongoing fade operation, but an on-
going fade operation may be cancelled by writing 0 to the
SFADE bit. Clearing the SFADE bit during an ongoing fade
operation changes the current immediately to the value
of SBL[4:0]. The number of counts to complete a fade
operation equals the difference between the old and new
SBL[4:0] settings. If SFADE is cleared, the current level will
change immediately without the fade delay. The rate of
fade may be changed dynamically by writing new values
to the SFADE1 and SFADE0 bits. The total fade time is
given by the number of steps between old and new back-
light values (see Table 5), multiplied by the rate of fade in
ms/step.
MB2, MB1, and MB0 [D2:D0]
These bits are used to set the number of LED drivers dedi-
cated to a main backlight function. This allows the device
to drive two different sets of LEDs with different settings
for use in products like clamshell-style mobile phones that
have a main display and a sub display with different light-
ing requirements. Note that any driver not selected for
the main display will automatically be assigned to the sub
display set. The code set by these three bits determines
which LED drivers are dedicated to the main display
according to the assignments listed in Table 12.
Table 12 — Main Display Driver Assignment Codes
MB2
MB1
MB0
Main Display Sub Display
LED Drivers LED Drivers
0
0
1
BL1 - BL5
none
0
1
0
BL1 - BL4
BL5
0
1
1
BL1 - BL3
BL4 - BL5
1
0
0
BL1 - BL2
BL3 - BL5
1
0
1
BL1
BL2 - BL5
000 and 110 through 111
BL1 - BL5
(default)
none
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