Don't really understand why you need a negative trigger in the first place....mainly because you haven't given us any information on the 'chip' that you're using. Might just be reading the datasheet wrong.

Unless you're confusing 'negative' with 'ground', sort of the way a lot of people think a 12v car battery has a +12v and a -12v, when in reality, it's +12v and common (or if you want the other way, common and -12v). LEDs, or circuits for that matter, don't GENERALLY require a positive and negative voltage, they need a voltage differential. Doesn't matter if you've got +5v/common (0v) or 105v/100v, both of them have a 5v differential.