LT3596 查看數據表（PDF） - Linear Technology

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LT3596

60V Step-Down LED Driver

Linear Technology 

LT3596

Pin Functions

FB (Pin 2): Feedback Pin. This pin is regulated to the

internal bandgap voltage. The maximum buck output

voltage is set by connecting this pin to a resistor divider

from VOUT .

EN/UVLO (Pin 4): Enable and Undervoltage Lockout Pin.

Accurate 1.5V falling threshold. UVLO threshold is pro-

grammed by using a resistor divider from VIN.

TSET (Pin 6): Thermal Regulation Pin. Programs the

LT3596 junction temperature at which LED current begins

to derate.

VREF (Pin 7): 2V Reference Output Pin. This pin sources

up to 200µA and is used to program TSET and CTRLM.

GND (Pin 9/Exposed Pad Pin 53): Ground Pin. This is

the ground for both the IC and the switching converter.

Exposed pad must be soldered to PCB ground.

NC (Pins 11, 12, 18, 22, 23, 26, 34, 35, 39, 41, 43): No

Connection Pins. Tie to ground if unused.

CTRLM (Pin 13): Master Control Pin. LED current derating

vs temperature is achievable for all channels if the voltage

on CTRLM has a negative coefficient using an external

NTC resistor divider from VREF .

ISET1, ISET2, ISET3 (Pins 14, 15, 16): LED Current Pro-

gramming Pin. Resistor to ground programs full-scale

LED current.

RT (Pin 17): Switching Frequency Programming Pin. A

resistor to ground programs switching frequency between

200kHz and 1MHz. For the SYNC function, choose the

resistor to program a frequency 20% slower than the

SYNC pulse frequency.

VOUT (Pin 19): Buck Output. This is the buck regulator

output voltage sense into the IC.

LED1, LED2, LED3 (Pins 20, 21, 24): Constant-Current

Sink Pin. These are three LED driver outputs, each contain-

ing an open collector, constant current sink. All outputs are

matched within ±1.5% and are individually programmed

up to 100mA using an external resistor at the ISET1-3 pin.

Outputs are rated to allow a maximum VOUT of 42V. Con-

nect the cathode of the LED string to LED1-3. Connect the

anode of the LED string to VOUT .

FAULT (25): Fault Detection Pin. Open-collector pin used

to report open LED faults. FAULT must be externally pulled

to a positive supply.

SYNC (Pin 27): External Clock Synchronization Pin. When

an external clock drives this pin, the buck regulator is

synchronized to that frequency. Frequency programmed

by the RT pin resistor must be at least 20% slower than

the SYNC pin clock frequency.

PWM1, PWM2, PWM3 (Pins 30, 29, 28): PWM Dimming

Control Pin. When driven to a logic high, the LED1-3 current

sink is enabled. Channels can be individually disabled by

tying PWM1-3 to ground. If PWM dimming is not desired

then the pin should be connected to VREF .

CTRL1, CTRL2, CTRL3 (Pins 33, 32, 31): Analog Dimming

Control Pin. This pin is used to dim the LED current in an

analog fashion. If the pin is tied to a voltage lower than

1.0V, it will linearly reduce the LED current. If unused the

pin must be connected to VREF .

BIAS (37): Supply Pin. This pin is the supply for an internal

voltage regulator for analog and digital circuitry. BIAS must

be locally bypassed with a 4.7µF capacitor.

DA (44): Catch Diode Anode. This pin is used to provide

frequency foldback in extreme situations.

BOOST (Pin 46): Boost Capacitor Pin. This pin is used to

provide a voltage above the input voltage when the switch

is on. It supplies current to the switch driver.

SW (Pin 48): Switch Pin. Connect the inductor, catch diode

and boost capacitor to this pin.

VIN (Pins 50, 51): Input Supply Pins. Pins are electrically

connected inside the package. VIN must be locally bypassed

with a 10µF capacitor to ground.

3596fa



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