JAJSFS7B July 2018 – February 2019 LM5180-Q1
ADVANCE INFORMATION for pre-production products; subject to change without notice.
Connect a diode-Zener clamp circuit across the primary winding to limit the peak SW node voltage after MOSFET turn-off below the maximum level of 100 V, as given by Equation 19.
Choosing the zener, DCLAMP, with clamp voltage of approximately 1.5 times the reflected output voltage, as specified by Equation 20, provides a balance between the maximum SW voltage excursion and the leakage inductance demagnetization time.
Select an ultra-fast switching diode or Schottky diode for DF with rated voltage greater than the maximum input voltage and with low forward recovery voltage drop.