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LT3591

White LED Driver with Integrated Schottky in 3mm × 2mm DFN

Linear Technology 

LT3591

PIN FUNCTIONS

VIN (Pin 1): Input Supply Pin. Must be locally bypassed.

GND (Pin 2): Ground Pin. Should be tied directly to local

ground plane.

SW (Pin 4): Switch Pin. Minimize trace area at this pin to

minimize EMI. Connect the inductor at this pin.

CAP (Pin 5): Output of the Driver. This pin is connected

to the cathode of internal Schottky. Connect the output

capacitor to this pin and the sense resistor from this pin

to the LED pin.

LED (Pin 7): Connection Point for the Anode of the First

LED and the Sense Resistor. The LED current can be

programmed by :

ILED

=

200mV

RSENSE

CTRL (Pin 8): Dimming and Shutdown Pin. Connect this

pin below 50mV to disable the driver. As the pin voltage

is ramped from 0V to 1.5V, the LED current ramps from

0 to ILED ( = 200mV/RSENSE). The CTRL pin must not be

left floating.

Exposed Pad (Pin 9): Ground. The Exposed Pad must

be soldered to PCB ground to achieve the rated thermal

performance.

BLOCK DIAGRAM

1

VIN

SHDN

VREF

1.25V

START-UP

CONTROL

–

PWM

COMP

A2

+

RSQ

Σ

RAMP

GENERATOR

4

SW

DRIVER

Q1

A3

R

OVERVOLTAGE

PROTECTION

OSCILLATOR

A1

RC

CC

A = 6.25

CAP

5

LED

7

CTRL GND

8

2

3591 F01

Figure 1. Block Diagram

3591f

5

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