Quick Start Procedure - Analog Devices EVAL-LT8376-AZ Demo Manual

PROGRAMMING LED CURRENT VIA CTRL PIN
The LT8376 uses the voltage across the current sense
resistor R1, and the voltage at the CTRL pin to program
the LED current. The maximum current sense resistor
voltage that can be programmed on the LT8376 is 100mV.
When V falls below 250mV, the LED current will be
CTRL
0A and when V is above 1.25, the LED current will
CTRL
be the maximum set by the current sense resistor. EVAL-
LT8376-AZ uses a 50mΩ current sense resistor, and a

QUICK START PROCEDURE

Evaluation board EVAL-LT8376-AZ is easy to set up to
evaluate the performance of the LT8376. Follow the pro-
cedure below:
1. With power off, connect a string of LEDs that will run
with forward voltage less than or equal to 36V (at 1.5A)
to the LED+ and LED– turrets on the PCB as shown in
Figure 1.
2. Set JP4 to EXT/ON and JP3 to ON for 100% always
on LED operation. Set JP2 to NO SSFM to run without
SSFM.
3. With power off, connect the input power supply to the
EMIVIN and GND turrets. Make sure that the DC input
voltage will not exceed 60V.
4. Turn the input power supply on and make sure the
voltage is between 43V and 57V for proper operation
at max LED current.
DEMO MANUAL EVAL-LT8376-AZ
voltage divider on the CTRL pin to regulate the LED cur-
rent to 1.5A. R8 and R15 set the voltage divider from
V pin to the CTRL pin. EVAL-LT8376-AZ will produce
REF
a maximum LED current of 2A when V
LED current can be analog dimmed to another current
level by adjusting R8 and R15. Please refer to the data
sheet for more details.
5. Observe the LED string running at the programmed
LED current.
6. To change the brightness with analog dimming, simply
attach a voltage source to the CTRL test point and set
the voltage between 0.25V and 1.25V. See data sheet
for details.
7. To change the brightness with external PWM dimming,
set JP4 to EXT/ON and JP3 to EXT. Attach a 1.5V rect-
angular waveform with varying duty cycle to the PWM
terminal.
8. To change the brightness with internally-generated
PWM dimming, set JP4 to INT and JP3 to INT. Adjust
the setting of the V
flathead screwdriver to toggle between 0% and 100%
PWM dimming duty cycle in 1/128 steps.
9. To enable spread spectrum frequency modulation, set
JP2 to SSFM.
> 1.25V. The
CTRL
variable resistor with a small
R1
Rev. 0
3