lt3591 Linear Technology Corporation, lt3591 Datasheet - Page 5

• Manufacturer Part Number: lt3591
• Description: White Led Driver With Integrated Schottky In 3mm X 2mm Dfn
• Manufacturer: Linear Technology Corporation

PIN FUNCTIONS
BLOCK DIAGRAM
V
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 :
IN
I
LED
(Pin 1): Input Supply Pin. Must be locally bypassed.
R
200
SENSE
mV
SHDN
START-UP
CONTROL
1.25V
V
REF
1
V
IN
OSCILLATOR
GENERATOR
RAMP
–
+
Figure 1. Block Diagram
A2
R
C
C
COMP
PWM
C
R
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 I
left fl oating.
Exposed Pad (Pin 9): Ground. The Exposed Pad must
be soldered to PCB ground to achieve the rated thermal
performance.
S
Q
A1
LED
–
+
+
DRIVER
A3
( = 200mV/R
8
+
CTRL
–
4
2
Q1
SW
GND
R
SENSE
OVERVOLTAGE
PROTECTION
A = 6.25
). The CTRL pin must not be
+
–
CAP
LED
3591 F01
5
7
LT3591
5
3591f