LT3491 LINER [Linear Technology], LT3491 Datasheet - Page 5

• Manufacturer Part Number: LT3491
• Manufacturer: LINER [Linear Technology]

BLOCK DIAGRA
PI FU CTIO S
SW (Pin 1/Pin 3): Switch Pin. Minimize trace area at this
pin to minimize EMI. Connect the inductor at this pin.
GND (Pins 2, 3, 4/Pin 2): Ground Pins. All three pins
should be tied directly to local ground plane.
V
bypassed.
CTRL (Pin 6/Pin 6): 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
be left floating.
IN
U
(Pin 5/Pin 1): Input Supply Pin. Must be locally
U
LED
( = 200mV/R
PIN NUMBERS CORRESPOND TO THE 8-PIN SC70 PACKAGE
SHDN
U
START-UP
CONTROL
(SC70/DFN)
W
SENSE
1.25V
V
). The CTRL pin must not
REF
5
V
IN
OSCILLATOR
GENERATOR
RAMP
Σ
Figure 1. Block Diagram
–
+
A2
R
C
C
COMP
PWM
C
LED (Pin 7/Pin 5): Connection Point for the Anode of the
First LED and the Sense Resistor. The LED current can be
programmed by :
CAP (Pin 8/Pin 4): 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.
EXPOSED PAD (NA/Pin 7): The Exposed Pad should be
soldered to the PCB ground to achieve the rated thermal
performance.
R
I
S
LED
Q
A1
=
–
+
+
200
R
DRIVER
SENSE
A3
mV
6
+
–
CTRL
1
Q1
SW
GND
PINS 2, 3, 4
R
OVERVOLTAGE
PROTECTION
A = 6.25
+
–
CAP
LED
3491 F01
8
7
LT3491
3491fa
5