Quick Start Procedure - Linear Technology LT8391EFE Demo Manual

DEMO MANUAL DC2345A
PERFORMANCE SUMMARY
PARAMETER
Input Voltage EMIVIN Range
Switching Frequency
I
LED
V range
LED
Open LED Voltage V
OUT
Typical Efficiency (100% PWM DC)
Internally-Generated PWM Dimming Range
Internally-Generated PWM Dimming Frequency
Peak Switch Current Limit Boost Region
Peak Switch Current Limit Buck Region

QUICK START PROCEDURE

Demonstration circuit DC2345A is easy to set up to evaluate
the performance of the LT8391 Follow the procedure below:
1. With power off, connect a string of LEDs that will run
with forward voltage less than or equal to 25V (at 2A)
to the LED+ and GND banana jacks on the PCB as
shown in Figure 1.
2. Connect the EN/UVLO terminal to GND.
3. Set JP1 to EXT/ON and JP3 to ON for 100% always-on
LED operation. Set JP2 to NO SPREAD/SYNC to run
without SSFM or external synchronization.
4. With power off, connect the input power supply to the
EMIVIN and GND banana jacks. Make sure that the DC
input voltage will not exceed 60V.
5. Turn the input power supply on and make sure the
voltage is between 4V and 60V for proper operation.
6. Release the EN/UVLO-to-GND connection.
2
Specifications are at T = 25°C
A
CONDITIONS
Operating V = 25V
LED
R3 = 100k
R1 = 0.05Ω 7.0V < PV < 60V V
IN
R5 = 1M R6 = 34.8k
R5 = 1M R6 = 34.8k
PV = 14V V = 25V I = 2.0A
IN LED LED
Operating JP3 = INT JP1 = INT
Operating JP3 = INT JP1 = INT R16 = 200k
R2 = 0.004Ω
R2 = 0.004Ω
7. Observe the LED string running at the programmed
LED current.
8. To change the brightness with analog dimming, simply
attach a voltage source to either the CTRL1 or CTRL2
terminal and set the voltage between 0V and 1.5V. See
data sheet for details.
9. To change brightness with external PWM dimming, set
JP1 to EXT/ON and JP3 to EXT. Attach a 3V rectangular
waveform with varying duty cycle to the PWM terminal.
10. To change brightness with internally-generated PWM
dimming, set JP1 to INT and JP3 to INT. Adjust the
setting of the VR1 variable resistor with a small flat-
head screwdriver to toggle between 0% and 100%
PWM dimming duty cycle in 1/128 steps.
11. To enable spread spectrum frequency modulation, set
JP2 to SPREAD ON.
MIN
4V
= 25V
LED
1/128
TYP MAX
60V
400kHz
2.0A
26V
29.7V
97%
100%
200Hz
12.5A
12.5A
dc2345af