I'm implementing a boost switching regulator based on a Texas LM5002 chip (datasheet), to get about 65V from a 12V supply. The design I've arrived at is shown below, inspired both from the data on the datasheet and the information here. I was not able to get all the parts with the necessary values, but I used the closest values I got my hands on. The design took into account an input current of about 50 mA to supply about 1mA on the output node.
simulate this circuit – Schematic created using CircuitLab
Problem is, when I tie 12V to the input, I get, for a few seconds, around 900V (???), before the output shorting to ground. What is exactly could be causing this? Have I got something wrong on my circuit?
EDIT: It appears I made a mistake on my original question while drawing the schematic, the actual value of R4 is 1.6k and not 100 ohms.