LTC3212 Datasheet, PDF (6/12 Pages) Linear Technology – RGB LED Driver and Charge Pump

LTC3212
Block Diagram
V_IN
12
900kHz
OSCILLATOR
1
11
CP
CM
10k
SHUT
DOWN
CPO
2
LEDEN
3
CONTROL LOGIC
3µA
ENR ENG ENB
–
+
I_SETB
4
–
+
I_SETR
5
–
+
I_SETG
6
GND
10
V_REF
TSD
ENB
LED
CURRENT
SOURCE
ENR
LED
CURRENT
SOURCE
ENG
OPEN
DETECTION/
AUTOSET
LED
CURRENT
SOURCE
DROPOUT
DETECTION
LEDB
9
LEDR
8
LEDG
7
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Operation
The LTC3212 uses a switched capacitor charge pump to
power three LEDs with a programmable regulated cur-
rent. The part powers up into 1x mode. In this mode V_IN
is directly connected to CPO. When powering up into 1x
mode, the LTC3212 charges the CPO capacitor to near
V_IN before directly connecting V_IN to CPO. This prevents
a large in-rush current. 1x mode provides maximum ef-
ficiency and minimum noise. The LTC3212 will remain
in this mode until one of the LED current source drivers

begins to drop out of regulation. When this drop out oc-
curs the LTC3212 will switch to 2x mode after a soft-start
period. The part will return to 1x mode when the part is
shut down and reprogrammed.
The current delivered through the LED load is controlled
by an internal programmable low dropout current source.
The current is programmed by resistors connected between
the I_SET(R,G,B) pins and GND.
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