I have a circuit that uses the LTM4600HV to create a 1.2V supply from 24V. Somehow this design made it into production, despite the fact that this Vin-Vout ratio is outside the range of the part. Not surprisingly, the circuit often oscillates. I've found that if I add a 499K resistor from Fadj to Vin (24V) I can stabilize the circuit. This results in a Ton time of 93ns, which is less than the 100ns minimum. I realize I'm off the map for this part, but how much further can I go without falling over the edge, and what dragons might I encounter on the way?
Update: I've gone with a 402K resistor, and therefore an 89ns pulse width without issue on a half-dozen units. I I also had to remove the recommended 100pF cap between Vout and Voset, and instead connect a 270pF cap from Voset to GND. I'm sure this slightly compromises transient response but it keeps the output stable.
Added the "Update" comments
[edited by: Charlie_99 at 4:24 PM (GMT 0) on 14 Dec 2018]