文档介绍：Partitioning and layout of a mixed signal PCB
Component placement and par- major problem is that you can- split as shown in Figure 1, what ployed.)
titioning, combined with rout- not route a trace over the split will be the current return path? If you must split the ground
ing discipline, are the keys to in the plane. If you do, you will Assuming that the two planes plane and run traces across the
ess in laying out a mixed- discover that both radiation and are connected together some- split, you should first connect
signal PCB—not the isolation of crosstalk will increase dramati- where, usually at a single point, the planes together at one loca-
the ground planes. cally. Traces routed across a slot the return current will have to tion, thus forming a bridge, as
flow in a large loop. HF cur- shown in Figure 3. Then, by
rents flowing in large loops pro- routing all the traces so that
duce radiation and high ground they cross at this bridge, you
inductance. Low-level analog will have provided a current re-
Analog ground plane currents flowing in large loops turn path directly underneath
are susceptible to interference. each of the traces, thereby pro-
An exceptionally bad configu- ducing a very small loop area.
ration is where the ground Other acceptable ways of
Trace plane is split and the two planes passing a signal over a split
are connected together o