Tool/software: Code Composer Studio
the code to UCD3138064 pulse width is basically unchanged, and the code is written to 3138064A pulse width frequently changes, and the range of change is 30-100ns
Is that normal?
It would be helpful to know things like what topology you are using, and what the conditions are, like input and output voltage and current, and whether the output voltage spec is being met.
Having said that, different parts, even of the same device can have different sensitivities to power supply noise. And certainly the UCD3138064A has different sensitivity than the 064.
We have a guide to recommended board layout techniques here 
