LTC3212 查看數據表（PDF） - Linear Technology

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LTC3212

RGB LED Driver and Charge Pump

Linear Technology 

LTC3212

Block Diagram

VIN

12

900kHz

OSCILLATOR

1

11

CP

CM

10k

SHUT

DOWN

CPO

2

LEDEN

3

CONTROL LOGIC

3µA

ENR ENG ENB

–

+

ISETB

4

–

+

ISETR

5

–

+

ISETG

6

GND

10

VREF

TSD

ENB

LED

CURRENT

SOURCE

ENR

LED

CURRENT

SOURCE

ENG

OPEN

DETECTION/

AUTOSET

LED

CURRENT

SOURCE

DROPOUT

DETECTION

LEDB

9

LEDR

8

LEDG

7

3212 BD

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 VIN

is directly connected to CPO. When powering up into 1x

mode, the LTC3212 charges the CPO capacitor to near

VIN before directly connecting VIN 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 ISET(R,G,B) pins and GND.

3212fb

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