LM25005: Negative Output, how to syncronize and enable with external signals

Hi,

I want to use the LM25005 as a negative Boost converter, Uin = 12V, Uout = -15V, I = 0.5A.

I attached the design pdf in this post.

My question is now, how can I manage to feed my enable signal and sync signal (both referred to Input ground) to the circuit?. In the design the AGND pin and also the RT pin are referred to -15V in my case (see circuit on fist page). But my signals are referred to input GND and not to -15V.

Could you please provide my more information about this toptic? 12Vneg_0A5_design.pdf