ltc3210-1 Linear Technology Corporation, ltc3210-1 Datasheet - Page 9

• Manufacturer Part Number: ltc3210-1
• Description: Main/cam Led Controller With 64-step Brightness Control In 3mm X 3mm Qfn
• Manufacturer: Linear Technology Corporation

OPERATIO
Power Management
The LTC3210-1 uses a switched capacitor charge pump
to boost CPO to as much as 2 times the input voltage up
to 5.1V. The part starts up in 1x mode. In this mode, V
is connected directly to CPO. This mode provides maxi-
mum effi ciency and minimum noise. The LTC3210-1 will
remain in 1x 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 LTC3210-1 will switch into 1.5x
mode. The CPO voltage will then start to increase and will
attempt to reach 1.5x V
dropout will cause the part to enter the 2x mode. The CPO
voltage will attempt to reach 2x V
will be reset to 1x mode whenever the part is shut down
or when ENC goes low.
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
phase. This sequence of charging and discharging the fl ying
capacitors continues at a constant frequency of 800kHz.
LED Current Control
The MLED currents are delivered by the four program-
mable current sources. 64 linear current settings (0mA
to 20mA, RM = 30.1k) are available by strobing the ENM
pin. Each positive strobe edge decrements a 6-bit down
counter which controls a 6-bit linear DAC. When the
SHUTDOWN
CURRENT
OR ENC
U
ENM
LED
BAT
up to 4.6V. Any subsequent
t PW ≥ 200ns
BAT
BAT
up to 5.1V. The part
Figure 1. Current Programming Timing Diagram
during the second
BAT
to minimize
BAT
t EN 150μs (TYP)
desired current is achieved ENM is stopped high. The
output current then changes to the programmed value
after 150μs (typ). The counter will stop when the LSB
is reached. The output current is set to 0 when ENM is
toggled low after the output has been enabled. If strobing
is started within 150μs (typ), after ENM has been set low,
the counter will continue to count down. After 150μs (typ)
the counter is reset.
The CLED current is delivered by a programmable current
source. Eight linear current settings (0mA to 380mA, RC
= 24.3k) are available by strobing the ENC pin. Each posi-
tive strobe edge decrements a 3-bit down counter which
controls a 3-bit linear DAC. When the desired current is
reached, ENC is stopped high. The output current then
changes to the programmed value after 150μs (typ). The
counter will stop when the LSB is reached. The output
current is set to 0 when ENC is toggled low after the output
has been enabled. If strobing is started within 150μs (typ)
after ENC has been set low, the counter will continue to
count down. After 150μs (typ) the counter is reset.
The full-scale output current is calculated as follows:
When both ENM and ENC are held low for more than
150μs (typ) the part will go into shutdown. See Figure 1
for timing information.
ENC resets the mode to 1x on a falling edge.
MLED full-scale output current
=
CLED full-scale output current
=
(
(
1.215V/(RM + 500)
1.215V/(RC + 500)
PROGRAMMED
CURRENT
t SD 150μs (TYP)
)
)
• 7700
• 535
ENM = ENC = LOW
LTC3210-1
32101 F01
32101fb
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