Jittery polyphase clock
View Patent ↗A plurality of clock signal phases are distributed to a circuit and at least one jitter source is coupled between at least two selected clock phases of the plurality of clock signal phases to introduce a jitter between at least the selected two clock signal phases. In a specific embodiment, the clock distribution system provides N clock phases and, if the phases have an order, there is one jitter source provided between each of the first N−1 phases and the following phase, so that each phase has a jitter relative to each other phase. Several implementations are possible for the jitter sources, which can be noise sources or pseudo-random noise sources, depending on which is easier to design and implement in a specific clock distribution system.
1. A clock distribution system, wherein a plurality of clock signal phases are disiributed to a circuit, the clock distribution system comprising:
at least one jitter source coupled between at least two selected clock phases of the plurality of clock signal phases to introduce a jitter between at least the selected two clock signal phases, where the jitter is a small phase shift;
wherein the at least one jitter source is a data-dependent pseudo-random noise generator, wherein the data-dependent pseudo-random noise generator is a circuit that introduces a delay that is dependent on a data calculation, wherein the data calculation completes after a duration that is dependent on the data in the data calculation.
2. The clock distribution system of claim 1 , wherein the plurality of clock signal phases is N clock signal phases, where N is an integer greater than one, wherein the at least one jitter source is N−1 jitter sources and wherein the selected clock phases for the N−1 jitter sources is selected such that a jitter is introduced between any two of the N clock signal phases.
3. The clock distribution system of claim 1 , wherein the jitter source is a random noise source.
4. The clock distribution system of claim 1 , wherein the jitter source is a pseudo-random noise source.
5. The clock distribution system of claim 1 , wherein the data-dependent pseudo-random noise generator comprises a pseudo-random number generator that generates a pseudo-random number to be used in the data calculation.
6. The clock distribution system of claim 1 , comprising an asynchronous FIFO control chain that generates the plurality of clock phases.
7. The clock distribution system of claim 6 , wherein the jitter source is a power supply to one or more stages of that asynchronous FIFO ring that varies a power supply voltage to at least one component of the one or more stages to jitter an output of the one or more stages.
8. A clock distribution system, wherein a plurality of clock signal phases are distributed to a circuit, the clock distribution system comprising:
at least one litter source coupled between at least two selected clock phases of the plurality of clock signal phases to introduce a jitter between at least the selected two clock signal phases, where the jitter is a small phase shift;
an asynchronous FIFO control chain that generates the plurality of clock phases;
a counterflow pipeline noise ring, wherein control signals flow in a counterflow relationship with control signals in the asynchronous FIFO control chain; and
at least one arbiter coupling the asynchronous FIFO control chain and the counterflow pipeline noise ring such that jitter is introduced in the control signals in the asynchronous FIFO control chain due to the arbitration process performed by the arbiter.
9. The clock distribution system of claim 8 , wherein the at least one arbiter is N−1 arbiters, where N is the number of phases in the plurality of clock phases.
10. The clock distribution system of claim 8 , wherein the at least one arbiter is an RGD arbiter.
11. The clock distribution system of claim 1 , wherein the jitter source is a variable delay having a delay related to the output of a low frequency oscillator.