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3. TECHNICAL BRIEF
3.10. LCD Backlight
The SC654 is a high efficiency charge pump LED driver using Semtech's proprietary charge pump
technology. Performance is optimized for use in single-cell Li-ion battery applications.
The SC654 is a write-only single wire interface. It provides access to up to 32 registers that control
device functionality.In this system, two sets of pulse trains are transmitted via the SPIF pin. The first
pulse set is used to set the desired address. After the bus is held high for the address hold period, the
next pulse set is used to write the data value. After the data pulses are transmitted the bus is held high
again for the data hold period to signify the data write is complete. At this point the slave device latches
the data into the address that was selected by the first set of pulses. The protocol for using this interface
is described in the following subsection.
SPIF
SPIF
SPIF
LGE Internal Use Only
V
B
A
T
2
2 .
u
C
2
5
8
L
C
D
_
B
L
_
C
T
R
L
V
A
2
0
0
C I
V
L
0
5
1
8
1
0
0
Y
5
0
0
F
R
< Fig 17. LCD Back light unit and Flash LED charge pump IC >
Address is set
Up to 32 rising edges
(0 to 31 pulses)
t = t
SU
t = t
t
SU
HI
t < t
HImax
Address is set to
register 02h
Interrupt
duration
t > t
HImax
< Fig 18. I2C Serial data port control method >
U
2
0
4
S
C
6
5
4
U
L
T
R
T
1
2
1
1
N I
O
U
T
1
3
B
L
1
5
1
4
S
P
F I
B
L
2
1
B
L
3
2
B
L
4
3
B
L
5
6
4
G
N
D
B
L
6
C
2
6
3
1
u
C
2
6
4
1
u
Up to 64 rising edges
(0 to 63 pulses)
t = t
HOLDA
t
t
HI
Address is set to
register 02h
t = t
HOLDA
t < t
Data written is
000010
t = t
HOLDA
- 42 -
Copyright © 2008 LG Electronics. Inc. All right reserved.
M
L
E
D
M
L
E
D
1
M
L
E
D
2
M
L
E
D
3
M
L
E
D
4
M
L
E
D
5
2
2 .
u
C
2
6
1
Data is written
t = t
HOLDD
LO
Data written is
000011
t
t = t
LO
HOLDD
LOmax
Address is set to register
03h (address and data are
now out of order)
t = t
HOLDD
Only for training and service purposes
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