LT3476 LINER [Linear Technology], LT3476 Datasheet - Page 5

• Manufacturer Part Number: LT3476
• Description: High Current Quad Output LED Driver
• Manufacturer: LINER [Linear Technology]

PI FU CTIO S
VC1, VC4, VC3, VC2, (Pins 1, 12, 13, 38): Error Amplifi er
Compensation Pin. When PWM is low, V
compensation capacitor to save state for next cycle.
LED1, LED2, LED3, LED4, (Pins 2, 5, 8, 11): Non-
Inverting Input of Current Sense Error Amplifi er. Connect
directly to LED current sense resistor terminal. Switcher
will regulate this node to a voltage of 0.1 • V
CAP node. Also connected to CAP node through external
sense resistor and to anode of LED string. Do not allow
this pin to fl oat independently of corresponding CAP input
pin. In applications where the LED current is low and the
PV
to LEDn.
CAP1, CAP2, CAP3, CAP4, (Pins 3, 4, 9, 10): Inverting
input of current sense error amplifi er. Connect directly to
other terminal of LED current sense resistor. Also con-
nected to output fi lter capacitor and cathode of external
Schottky rectifi er. CAP greater than the overvoltage protect
threshold will inhibit switching.
R
connected to GND to program oscillator frequency.
REF: (Pin 7): Reference Output Pin. Connect to V
to get full-scale LED current. Connect to resistor dividers
to program V
to local GND with 0.1μF capacitor.
V
Current Adjustment Pin. Sets voltage across external sense
resistor between CAPn and LEDn. Connect directly to
REF for full-scale threshold of 105mV, or use signal vales
between GND and REF to modulate LED current. V
input range is 1.25V maximum.
ADJ4
T
IN
U
(Pin 6): Oscillator Programming Pin. Place resistor
changes widely, connect the output fi lter capacitor
, V
ADJ3
U
, V
ADJ
ADJ2
pins to values lower than 1.05V. Bypass
, V
U
ADJ1
, (Pins 14, 15, 36, 37): LED
C
pin fl oats external
ADJ
below the
ADJ
ADJ
pin
pin
PWM4, PWM3, PWM2, PWM1, (Pins 16, 17, 34, 35):
Signal low turns off the channel—disables the main
switch, reduces quiescent supply current to the channel,
and causes the V
impedance.
SHDN (Pin 18): Shutdown Pin. Higher than 1.5V turns
the device on.
NC (Pins 19, 20, 21, 30, 31, 32): Not Used. Connect to
GND (Pin 39) for better heat dissipation.
SW4, SW3, SW2, SW1, (Pins 22, 23, 24, 25, 26, 27, 28, 29):
Switch Pin. Connect to external inductor and anode of external
Schottky rectifi er. Minimize area of SW trace and use a
GND plane to reduce EMI. Adjacent pins of same name
are internally connected.
V
passed.
GND (Pin 39): Signal and Power GND. Solder Exposed
Pad directly to ground plane. The Exposed Pad metal of
the package provides both electrical contract to ground
and good thermal contact to the printed circuit board.
It must be soldered to the circuit board for proper
operation.
IN
(Pin 33): Input Supply Pin. Must be locally by-
C
pin for the channel to become high
LT3476
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