Provided is a downhole perforating device, a well system, and a method for perforating a well system. The downhole perforating device, in one aspect, includes a perforating structure for surrounding at least a portion of an outer surface of a wellbore casing. The downhole perforating device, according to this aspect, includes one or more perforation elements at least partially embodied within the perforating structure, the one or more perforation elements positioned to perforate the wellbore casing to an inside thereof, and electronics at least partially embodied within the perforating structure, the electronics for triggering the one or more perforation elements.