The MAX17681 iso-buck involves driving a transformer which has leakage Inductance and parasitic winding capacitance, thus making the current oscillations last longer. It is important to also specify the transformer for these prasitics. The feedback pin FB is connected to the transformer primary winding through a resistor divider.
The guidance for specifying the transformer is as follows:
•Generate basic electrical specs with the MAX17681 EESIM tool
•Include isolation specs
•Recommended Sizes:
1W- EP5 or similar 2W- EP7 or similar
3W- EP10 or similar 5W- EP13 or similar
•Leakage Inductance(Llk):
Higher leakage = poor output voltage regulation and low frequency current ringing
Recommended: 0.5-1% of primary Lm to achieve high frequency current ringing that settles fast within the blanking time of MAX17681/2.