The CGS31 is a very standard pseudo-random digital noise source with a few enhancements. Instead of running a fixed high frequency clock, a VCO is used instead, allowing for unusual sweeps, and for reducing the speed right down to a series of random pulses. The internal linear VCO can also be bypassed so an external source such as a 1V/Oct. It has pink and white noise outputs, and two separate (unique) digital outputs for use in triggering other circuits.
CGS31 Datasheet and Build Guide