Contents
Where to place analog and digital ICs on a PCB?
The analog portion of your board should be placed over the analog ground plane while maintaining isolation between grounds across the PCB. The same applies to digital ICs: they should be placed over their own ground plane.
Why are two planes on an analog PCB important?
It is also important that these two planes do not overlap with each other, as that could cause capacitive coupling of noise from the digital ground into the analog. By carefully placing your components, you can establish regions for your separate circuitry that will allow you to not overlap your planes.
Can a PCB be a purely digital system?
Nowadays, you cannot get away with running a purely digital or analog system in a complicated electronic product. Mixed signal PCBs are the norm, making old layout strategies obsolete. We live in a nonlinear analog world, and things only really become digital or linear on paper.
Is it important to separate analog and digital ground planes?
Separating analog and digital ground planes is a contentious design practice that can create power integrity and signal integrity problems. Separating the ground planes is less important than routing over the gap between two ground plane regions.
Why are mixed signal ICs need different grounding techniques?
To further complicate the issue, mixed-signal ICs have both analog and digital ports, adding to the confusion with respect to proper grounding techniques. In addition, some mixed-signal ICs have relatively low digital currents, while others have high digital currents. In many cases, these two types require different treatment for optimum grounding.
What’s the difference between analog and digital ICs?
Depending on how circuit elements in your IC are mixed, the output signal from an analog IC can exhibit strong nonlinearity. Meanwhile, digital ICs are nonlinear by definition, and logic processing circuits are really piecewise nonlinear.