Linear Technology LT3791, 4.7V-60V input to drive 25V of LEDs at 2A (scalable to 100W) DC1666A DC1666A 数据表

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dc1666af

DEMO MANUAL DC1666A

LT3791

Four-Switch Buck-Boost 

LED Driver Controller

Demonstration circuit DC1666A is a synchronous four-

switch buck-boost LED driver controller. It accepts an 

input voltage from 4.7V to 60V, and drives up to 25V of 

LEDs at 2A. DC1666A features both PWM and analog 

dimming of the LED string. It has an OPENLED flag that 

indicates when the LED string has been removed and it 

has a SHORTLED flag that indicates that the output has 

been shorted to GND. In both cases, the IC remains in 

control and well protected.
DC1666A features very high efficiency at 300kHz switching 

frequency and continuous conduction mode (C

CM

). The 

synchronous four-switch topology both steps up and steps 

down voltage while regulating up to 50W of constant LED 

output current at efficiencies up to 98%. The circuit can 

be altered for applications requiring over 100W of LEDs. 

An optional SYNC terminal is provided for synchronizing 

to an external clock and CLKOUT terminal provides a 

source to sync another converter to the internal clock of 

the LT

®

3791.

Three sense resistors provide constant output current 

control and monitoring, peak switch current control, and 

DC input current limit and monitoring. The I

SMON

 and 

I

VINMON

 outputs tell the user how much current is flowing 

through the output and input sense resistors.
Small ceramic input and output capacitors are used to 

save space and cost. The open LED overvoltage protection 

uses the ICs constant voltage regulation loop to limit the 

output to approximately 28.3V if the LED string is opened.
For low input voltage operation, the CTRL pin voltage is 

reduced as the input voltage drops below 6.5V, reducing 

LED brightness and restraining the peak switch currents 

in order to limit inductor and switch size. UVLO turns the 

LEDs off when V

IN

 drops below 4.7V. When input rises 

above 57.6V, overvoltage lockout turns the switches off 

to protect them and they turn back on when V

IN

 drops 

below 56.2V.
DC1666A PWM dimming is simple. The PWM dimming 

MOSFET turns the LED string on and off with 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 Applications Information 

section of the LT3791 data sheet. Analog dimming is also 

simple with a simple voltage source on the CTRL terminal.
Modifications can be made to DC1666A in order to convert 

the board to higher or lower power or from an LED driver 

to a constant voltage regulator or battery charger. Please 

consult the factory or the LT3791 data sheet for details.
The LT3791 data sheet gives a complete description of 

the part, operation and applications information. The 

data sheet must be read in conjunction with this demo 

manual for demonstration circuit DC1666A. The LT3791 

is assembled in a 38-lead plastic TSSOP package with 

a thermally enhanced ground pad. Proper board layout 

is essential for maximum thermal performance. See the  

Layout Considerations section in the data sheet. 
Design files for this circuit board are available at  

L

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