ZHCSJ08A November 2018 – July 2019 LM25180-Q1
ADVANCE INFORMATION for pre-production products; subject to change without notice.
Connect a diode-Zener clamping circuit across the primary winding to limit the peak switch-node voltage after MOSFET turn-off below the maximum level of 65 V, as given by Equation 20.
Choosing the zener, DCLAMP, with clamp voltage of approximately 1.5 times the reflected output voltage, as specified by Equation 21, 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.