LT3591

5

3591f

BLOCK DIAGRAM

PIN FUNCTIONS

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 :

I

mV

R

LED

SENSE

=

200

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

left floating.

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

be soldered to PCB ground to achieve the rated thermal

performance.

4

–

+

R

SW

CAP

1

Q

S

DRIVER

Σ

OVERVOLTAGE

PROTECTION

RAMP

GENERATOR

OSCILLATOR

1.25V

START-UP

CONTROL

SHDN

Q1

R

5

LED

3591 F01

CTRL

GND

7

82

–

+

A = 6.25

A1

A2

A3

PWM

COMP

Figure 1. Block Diagram