In the world of electronics
, and IC
design in particular, the clock tree
is the distribution network
along which the clock signal
is supplied to all parts of the circuit
The origin of the clock signal could be directly from an external crystal oscillator, but this is likely to be used by an on-chip PLLand clock generator to create the clock signals required by the different clock domains within the IC. Either way, the clock signal is a point source and must be distributed to all the circuit's sequential logic gates.
Clock trees are so-named because the distribution network can be visualised as tree branches emanating from the tree trunk, (symbolising the clock source, of course).
Why do we need a clock tree?
A clock distribution network
is required to minimise clock skew
within the circuit
, thereby facilitating
the correct timing
operation of the circuit
How a clock tree is implemented.
A clock tree
can be balanced
through the use of a hierarchy
s which helps to reduce the capacitive load
seen by any driver
in the clock network
s also introduce delay
into the clock tree
, the amount of which can be determined on a 'branch by branch' basis. This hierarchical organisation
s is analagous to the way tree branch
es divide as they grow further out from the tree trunk