Chapter 38: Layout and Grounding for Analog and Digital Circuits

The ratio of digital designers to analog designers is increasing. This is not a news flash. Although the emphasis on digital design is providing significant advances in electronic end products, there is still and will always be a portion of circuit design that interfaces with the analog or real world. Could it be possible that analog layout differs from digital layout techniques? There is some similarity in layout strategies between these two domains. The differences can make an easy circuit layout design less than optimum if you are trying to achieve good results. In this chapter, we will discuss five topics. The first topic covers fundamental similarities and differences between analog and digital layout. Then we will talk about the hidden components (resistors, inductors, and capacitors) embedded in your PC board. The next section of this chapter will talk about how to improve your A/D converter accuracy and resolution. Getting another converter will not help here. Focusing on the interaction between the PCB and your converter will improve your results. This will be followed by the fourth section where we will discuss two-layer layout techniques. Finally, we will end with an example of how to do a poor layout and then how to fix it.