3
Rev. 0
QUICK START PROCEDURE
Evaluation board EVAL-LT8355-1-AZ is easy to set up
to evaluate the performance of the LT8355-1. Follow the
procedure below.
1. With power off, connect a string of LEDs that will
run with forward voltage less than or equal to 72V
(at 450mA) to the LED1+ and LED1– (boost) turrets
and another string of LEDs that will run with forward
voltage less than or equal to 30V (at 1A) to the LED2+
and LED2– (buck-boost) turrets as shown in Figure 2.
2. With power off, connect the input power supply to the
PVIN and GND turrets. Make sure that the DC input
voltage will not exceed 18V.
3. Turn the input power supply on and make sure the
voltage is between 8V and 18V for proper operation
at max LED current.
4. Observe the LED strings running at the programmed
LED current.
5. To change the brightness with
analog dimming
, the
CTRL1 pin is used for channel 1 and CTRL2 and IADJ2
pins are used for channel 2. The product of the offset
CTRL and IADJ pin voltages sets the current when the
two voltages vary between 0.5V and 1.5V. Please refer
to data sheet for more details.
6. To change the brightness with
external PWM dimming
,
attach a rectangular waveform with varying duty cycle
to the respective PWM turret for channel 1 and chan-
nel 2. The ON and OFF voltages should be above 1.6V
and below 0.4V, respectively.
7. To change the brightness with
internally-generated
PWM dimming
, adjust the voltage at the respec-
tive PWM pin for channel 1 and channel 2 between
0.5V and 1.5V to vary the duty ratio of the internal
PWM generator.
