Performance Summary; Quick Start Procedure - Linear Technology DC1784A Demo Manual

DEMO MANUAL DC1784A

performance summary

PARAMETER
Input Voltage PVIN Range
Switching Frequency
I CH1, CH2, CH3
LED
Low PVIN I (CTRL foldback)
LED
V Range CH1, CH2, CH3
LED
Open LED Voltage CH1, CH2, CH3
Typical Efficiency (100% PWM Duty Cycle)
PVIN Under Voltage Lockout (Falling Turn-Off)
PVIN Under Voltage Lockout (Rising Turn-On)
INTV
CC
Peak Switch Current Limit CH1, CH2, CH3

Quick start proceDure

DC1784A is easy to set up to evaluate the performance of
the LT3797EUKG. Follow the procedure below:
1. Connect three strings of LEDs that will run with forward
voltage less than 50V (at 1A), but greater than PVIN,
+
to the LED and GND terminals on the PCB as shown
in Figure 1.
2. Connect the EN/UVLO terminal to GND.
3. With power off, connect the input power supply to the
PVIN and GND terminals. Make sure that the PVIN DC
input voltage does not exceed 40V (or V
4. Turn the input power supply on and make sure the
voltage is between 2.5V and 40V (or V
2
CONDITIONS
Operating V = PVIN
IN
R1 = 47.5k
R2, R3, R4 = 0.25Ω 10.5V < PVIN < V
R2, R3, R4 = 0.25Ω PVIN = 4.0V
R2, R3, R4 = 0.25Ω PVIN = 6.0V
R2, R3, R4 = 0.25Ω PVIN = 9.0V
R8, R9, R10 = 23.2k R14, R15, R16 = 1M
R8, R9, R10 = 23.2k R14, R15, R16 = 1M
PVIN = 14V V = 50V and I
LED LED
R26 = 100k and R27 = 105k
R26 = 100k and R27 = 105k
Operating
R11, R12, R13 = 0.008Ω
5. Connect the PWM1-3 input terminals to INTV
to enable 100% brightness control when EN/UVLO is
released.
6. Release the EN/UVLO-to-GND connection.
7. Observe the LED strings running at the programmed
LED current.
8. To change the brightness with analog dimming, sim-
ply attach a voltage source on any or all of the CTRL
terminals and set the voltage(s) between 0V and 1.5V.
). See data sheet for details.
LED
9. To change brightness with PWM dimming, remove the
). connection from PWM1-3 to INTV
LED
a 3.3V to 5V rectangular waveform with varying duty
cycle.
VALUE (TYPICAL)
2.5V to V
LED
310kHz
(40V) 1.0A
LED
280mA
525mA
890mA
PVIN < V
LED
55V
= 1A CH1, CH2, CH3 93.5%
2.5V
2.6V
7.5V
12.5A
(Up to 40V)
< 50V
or V
CC REF
or V and attach
CC REF
dc1784af