I am trying to simulate non isolated buck converter with LT8315 ic given in datasheet as application example of LT8315 in LTspice software. the output is not regulated and does not give 12 volts as per given design . could you please tell what could have gone wrong . what is the need of diode D4 zener here? if i dont put the diode D4 then output wont be regulated ? what should be the transient profile for this simulation ? a 100 ohm resistor(12/0.120) at the output instead of Diode D4 does not work.