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ADP2441 - VCC goes low when VIN > 8.5V Latch Up


I have two ADP2441 regulators on the PCB one at 3.3V (which is working as expected) and one at 5.8V (Schematic included).

When the second regulator is unloaded it behaves normally (reaching regulation at approx VIN= 7V) until VIN > approx 8.5V at this point the internal regulator VCC drops to 1.3V, switching ceases, and the  circuit current draw jumps approx 25 ma. The regulator only recovers if the circuit is power cycled. If there is a load of around 10mA this behaviour does not occur.

So far I have tried replacing the ADP2441, the bypass capacitor and reducing the switching frequency all to no avail.

EN is tied to VIN.

PGOOD is left floating.

I have attached to Scope plots, the first is with VIN = 10V supplied by a bench top power supply and just turning the unit on. The second is slowing increasing VIN until the behaviour occurs.

In both plots all Voltage Div is 5V / Div.

CH1 = ADP2441 VCC pin.

CH2 = ADP2441 Pin 8


CH4 = VOut

I'm really hoping you can help me out, as I'm completely out of ideas.