The LT3518 is a current mode DC/DC converter with an internal 2.3A, 45V switch specifically designed to drive LEDs. The LT3518 operates as a LED driver...
LT3518 on Analog.com
Is the Soft Start function of the LT3518 operates only at the initial start up, or it operates wch time the PWM wake up the driver?
I have to correct myself on this one. LT3518 will go to start up mode when Vfb goes below 1V.
When the PWM signal shuts off the LED current Vout is maintained which keeps LT3518 going to SS mode.
Thanks. Now it is clear.