LT3519 LINER [Linear Technology], LT3519 Datasheet - Page 6

• Manufacturer Part Number: LT3519
• Description: LED Driver with Integrated Schottky Diode
• Manufacturer: LINER [Linear Technology]

PIN FUNCTIONS
LT3519
GND (Pins 1, 8, 9, 16): Power Ground and Signal Ground.
Tie to GND plane for best thermal performance.
OPENLED (Pin 2): Open LED Status Pin. The OPENLED
pin asserts if the FB input is greater than the FB regulation
threshold minus 60mV (typical). The pin must have an
external pull-up resistor to function. When the PWM input
is low and the converter is idle, the OPENLED condition
is latched to the last valid state when the PWM input was
high. When the PWM input goes high again, the OPENLED
pin will be updated. This pin may be used to report an
open LED fault.
PWM (Pin 3): Pulse Width Modulated Input. A signal
low disables the oscillator and turns off the main switch.
PWM has an internal pull-down resistor. Tie PWM pin to
V
SHDN/UVLO (Pin 4): Shutdown and Undervoltage Lockout
Pin. An accurate 1.22V falling threshold with externally
programmable hysteresis detects when power is okay to
enable switching. Rising hysteresis is generated by the
external resistor divider and an accurate internal 2μA pull-
down current. Above the 1.25V (nominal) rising threshold
(but below 6V), SHDN/UVLO input bias current is sub-μA.
Below the falling threshold, a 2μA pull-down current is
enabled so the user can defi ne the hysteresis with external
resistor selection. Tie to 0.4V or less to disable device and
reduce V
to V
is less than 6V.
V
bypassed with a 1μF ceramic capacitor (or larger) placed
close to it.
6
REF
IN
IN
(Pin 5): Input Supply Pin. This pin must be locally
if not used.
, but do not tie it to a voltage higher than V
IN
quiescent current below 1μA. Pin may be tied
IN
if V
IN
SW (Pin 6): Switch Pin. Connect the inductor at this pin.
Minimize the trace at this pin to reduce EMI.
ANODE (Pin 7): Internal Schottky Anode Pin.
CATHODE (Pin 10): Internal Schottky Cathode Pin.
ISP (Pin 11): Current Sense Resistor Positive Pin. This
input is the noninverting input of the internal current
sense amplifi er.
ISN (Pin 12): Current Sense Resistor Negative Pin. This
input is the inverting input of the internal current sense
amplifi er.
FB (Pin 13): Voltage Loop Feedback Pin. It is used to
connect to output resistor divider for constant voltage
regulation or open LED protection. The internal trans-
conductance amplifi er will regulate FB to 1.22V (nominal)
through the DC/DC converter. If the FB input is regulating
the loop, the OPENLED pull-down is asserted. This action
may signal an open LED fault. Do not leave the FB pin
open. If not used, connect to GND.
CTRL (Pin 14): Current Sense Threshold Voltage Adjust-
ment Pin. This pin sets the threshold voltage across the
sense resistor between ISP and ISN. Connect directly
to the V
threshold of 250mV, or use a voltage between 0.1V and
1.2V to linearly adjust the threshold. Tie CTRL pin to the
V
V
pin can supply up to 100μA.
REF
REF
pin if not used.
(Pin 15): Reference Output Pin. Typically 2V. This
REF
pin or a voltage above 1.2V for full-scale
3519f