Linear Technology LT3755, Быстрый старт

Страница: 2 / 11

QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1268A-A, 1268A-B
HIGH VOLTAGE LED CONTROLLER
2
Table 1.
Typical Performance Summary for DC1268A-A/B
PARAMETER CONDITION VALUE (TYPICAL)
Input Voltage PVIN Range Operating 8V-40V
Switching Frequency R8 = 28.7k 400kHz
I
LED
1A
Maximum Output Voltage - Open LED Voltage 56V
Efficiency PVIN=12V V
LED
=50V I
LED
=1A 93%
Under Voltage Lockout 8V
Peak Switch Current Limit RS1 = 0.015 Ω 6.6A
QUICK START PROCEDURE
Demonstration circuit 1268A-A, 1268A-B is easy to
set up to evaluate the performance of the LT3755,
LT3755-1. Follow the procedure below:
NOTE:
Make sure that the PVIN DC input voltage
does not exceed 40V.
1.
Connect a string of LEDs with forward voltage
less than 55V, but greater than the PVIN voltage,
to the LED+ and LED- (Boost) terminals on the
PCB as shown in Figure 1.
2.
Connect the shutdown terminal to GND.
3.
With power off, connect the PVIN power supply
to the PVIN and GND terminals within the ranges
specified on the PCB.
4.
Connect the PWM terminal. If PWM is not used,
connect PWM to a 5V source or to IntVcc on the
PCB. PWM must be pulled high to work. For –B,
the SYNC input can be left floating.
5.
Turn the PVIN power supply on.
6.
Release the shutdown/GND connection.
7.
Observe the LED string running at the pro-
grammed LED current.
8.
For PWM dimming, connect a PWM 100Hz or
higher signal to the PWM terminal.
9.
Observe the reduction of brightness in the LED
string when PWM dimming.