LT8608 or LT8609 with negative output


I am trying to use the LT8608 as a positive to negative voltage converter as described for example linear technology design note 1021.

The simulation in LTSpice works fine, producing -6V from 15V supply. Necessary output current is less than 1A. 

But the prototype isnt working, it immediately draws a high current from the power supply and the LT8608 controller is destroyed. I already checked the voltage ratings of the capacitors and inductor. 

When I change the controller from LT8608 to LT8609A, the same prototype is working fine. 

Is there any major difference between these two controllers which is relevant for this behaviour?

What could be the reason that the LT8608 is drawing such a high current right at the beginning?

Many thanks in advance

Schematic in LTSpice: