LTC3208EUH Linear Technology, LTC3208EUH Datasheet - Page 9

• Manufacturer Part Number: LTC3208EUH
• Description: IC,Laser Diode/LED Driver,CMOS,LLCC,32PIN,PLASTIC
• Manufacturer: Linear Technology

BLOCK DIAGRA
OPERATIO
Power Management
The LTC3208 uses a switched capacitor charge pump to
boost CPO to as much as 2 times the input voltage up to
5V. The part starts up in 1x mode. In this mode, V
connected directly to CPO. This mode provides maximum
effi ciency and minimum noise. The LTC3208 will remain in
this mode until an LED current source drops out. Dropout
occurs when a current source voltage becomes too low
for the programmed current to be supplied. When dropout
is detected, the LTC3208 will switch into 1.5x mode. The
CPO voltage will then start to increase and will attempt to
reach 1.5x V
cause the part to enter the 2X mode. The CPO voltage will
attempt to reach 2x V
ENRGBS
CAMHL
V
V
V
DV
BAT1
BAT2
BAT3
R
SDA
BAT
SCL
REF
CC
30
24
12
13
14
28
11
10
9
up to 4.5V. Any subsequent dropout will
U
BAT
up to 5V. The part will be reset to
W
OSCILLATOR
900kHz
1.215V
+
–
+
–
SLAVE REG
REGISTER
CONTROL
MASTER/
SHIFT
LOGIC
RED
23
CHARGE PUMP
BAT1,2
GRN
22
are
C1P
31
BLUE
21
1x mode whenever a DAC data bit is updated via the I
port or on the falling edge of the CAMHL signal.
A two-phase nonoverlapping clock activates the charge
pump switches. In the 2x mode the fl ying capacitors are
charged on alternate clock phases from V
input current ripple and CPO voltage ripple. In 1.5x mode
the fl ying capacitors are charged in series during the fi rst
clock phase and stacked in parallel on V
second phase. This sequence of charging and discharging
the fl ying capacitors continues at a constant frequency of
900kHz.
The currents delivered by the LED current sources are
controlled by an associated DAC. Each DAC is programmed
via the I
The value of R
3
C1M
CAM1
27
1
2
C port. The full scale DAC currents are set by R
CAM2
2
C2P
29
REF
CAM3
3
is limited to the range of 22k to 30k.
MAIN CURRENT
CAM CURRENT
SUB CURRENT
AUX CURRENT
RGB CURRENT
SOURCES
SOURCES
SOURCES
SOURCES
SOURCES
CAM4
4
C2M
ENABLE CP
26
AUX4
8
4
2
4
4
AUX3
7
3208 BD
LTC3208
25
32
15
16
17
18
19
20
5
6
BAT
BAT
SUB2
SUB1
AUX1
AUX2
GND
CPO
MAIN1
MAIN2
MAIN3
MAIN4
to minimize
during the
3208fa
9
REF
2
C
.