LM2678 3.3V 100% Duty Cycle?

[aquacomdev]

I'm using the LM2678 3.3V output version of this chip. My issue is that the output voltage follows the input voltage. There aren't any apparent shorts. One thought is that for some reason the chip is working at 100% duty cycle. The other thought was that the chip was dead. We're swapping it out right now. Anyone have any other ideas?

I've attached the pdf w/ schematic. I just hooked and o-scope to the node between the inductor and diode. It almost looks DC. When I zoom in I can see what looks like 95% duty cycle switching between 15.11 & 15.34 w/ input voltage of 16V.

We're using the typical design circuit on pg 1. Except different cap values for 3.3V

 

[FvM]

95% duty cycle sounds rather like you missed to connect the feedback pin. But it still may be a defective chip.