Clock distribution using cooperative ring oscillators

This paper presents a new form of integrated ring oscillator, the Cooperative Ring Oscillator (CRO), in which the controllable delay elements are distributed throughout a VLSI chip. Specifically, each stage of the CRO consists of many electrically parallel delay elements that are spatially distributed. The high degree of parallelism in the CRO provides strong signal aggregation that significantly reduces the skew within each clock phase. The CRO performs both clock generation and clock delivery, thus unifying the tasks of the oscillator, clock buffers, and distribution network into a single circuit. The strength of the CRO technique is that it can deliver multiple, low-skew clock phases to all areas of a large VLSI device at a cost in chip resources comparable to that of current single-phase clock distribution techniques. This strength creates the opportunity for system designers to make extensive use of multi-phase logic techniques to improve system performance.