DC1268B-B - LT3755EUD-2, LT3755EUD-1 Evaluation Kit Quick Start Guide

Features

  • DC1268B-B -LT3755EUD-2, LT3755EUD-1 Evaluation Kit
  • Disclaimer: Linear Technology cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Linear Technology product. No circuit patent licenses are implied. Linear Technology reserves the right to change the circuitry and specifications without notice at any time.

Typical Application

DC1268B-B
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Description

Demonstration circuit 1268B-A, 1268B-B is a high
voltage and high current LED driver controller. The
VIN pin input voltage is as high as 40V. The LED output
voltage on this board is as high as 60V but can be
set as high as 75V. The demonstration circuit is assembled as a boost topology from 8-40V input and
up to 54V LED output at 1A with an open LED status
pin (-A) or a sync input pin (-B). DC1268B features
PWM dimming, analog dimming, shutdown, and
open LED overvoltage protection. Efficiency at 12VIN
is as high as 93% for 50W output.
The switching frequency is set at 400kHz to accommodate
the automotive switching frequency range.
Small ceramic input and output capacitors are used
to save space and cost and a high voltage 60V external
power switch and a 60V catch diode are used for
up to 54W (54V at 1A) output as assembled. The
open LED overvoltage protection will limit the output
to approximately 56V if the LED string is opened. For
low input voltage operation, the CTRL pin voltage is
reduced as the input voltage drops below 9V, reducing
LED brightness and restraining the peak switch
currents in order to limit inductor and switch size.
UVLO turns the LEDs off when VIN drops below 8V.
DC1268B PWM dimming is simple. The boost topology
LED string returns to the LED- terminal and the
PWM dimming MOSFET turns the LED string on and
off given an input to the PWM dimming terminal. For
the highest pwm dimming ratio, it is recommended to
use 100Hz as a pwm dimming frequency. Information
regarding PWM dimming ratios and performance can
be found in the LT3755-2/-1 datasheet in the applications
section.
Soft-start is provided with a simple and small capacitor
to maintain control of the switch current during
turn on for high power designs.
Modifications can be made to the DC1268B in order
to convert the board from a boost topology LED
driver to any other topology. Buck-boost mode, buck
mode, and SEPIC schematics are provided in the
datasheet. Please consult the factory or LT3755-2/-1
datasheet for details regarding how to customize the
DC1268B or how to design different topologies for
custom specifications.
The LT3755-2, LT3755-1 datasheet gives a complete
description of the part, operation and applications
information. The datasheet must be read in conjunction
with this Quick Start Guide for demonstration
circuit 1268B-A, 1268B-B. The LT3755-2, LT3755-1 is
assembled in a small 16-lead plastic QFN package
with a thermally enhanced ground pad. Proper board
layout is essential for maximum thermal performance.
See the datasheet section ‘Layout Considerations’.
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Packaging

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Order Info

Evaluation Kits

Part Number Description Price
DC1268B-A LT3755EUD-2 Demo Board| 40V/75V Full-Featured LED Controller $175.00
DC1268B-B LT3755EUD-1 Demo Board | 40V/75V Full-Featured LED Controller $175.00
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Applications

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