Clock Tree 101

A clock tree is a clock distribution network within a system or hardware design. It includes the clocking circuitry and devices from clock source to destination.

The complexity of the clock tree and the number of clocking components used depends on the hardware design. Since systems can have several ICs with different clock performance requirements and frequencies, a "clock tree" refers to the various clocks feeding those ICs.

It's often the case that a single reference clock will be cascaded and synthesized into many different output clocks, resulting in a diagram that looks a bit like a sideways tree trunk. The "trunk" is the reference clock and the "branches" are the various output clocks.

Fig.1 - Example "Clock Tree"