When making custom PCB projects, one of the common practice by beginners is to have all the components on a single schematic and transferring over to the PCB file. This practice normally does not cause any problem, when you’re dealing with small scale design with less than 50 components as below.
But design could get complicated when you’re having hundreds or more components in your schematic. You’ll also need to take into consideration of various functionalities in a single design. For example when you’re building a general purpose controller where you have the microcontroller, ethernet, memory chips, power, inputs, and outputs.Creating a single schematic with all the components fitted in could pose some problems for ease of troubleshooting and assembly.
When you’re designing complicated custom PCB, chances are your support team have to handle faulty repairs down the line. Having a single sheet schematic poses two potential problems. Firstly, it is unlikely the repair team have the same design knowledge. It will be easier to segregate the design into modules for ease of understanding. Secondly, there could be some proprietary part of the design that is strictly confidential, even to the support team. Here’s where a modular design like this helps.
Each module is then linked to a single schematic sheet. Below shows a single sheet with microcontroller and components for its primary functionality.
Note that you could also form a system for the designator so that it is easy to locate components on the board and also identify components to the module it belongs. My practice in building custom PCB is I separate components from the different module by the leading number in the designator. Example, U100, U101 indicates IC components for module 1 and U200, U201 are for module 2. This method of design has served me well in project maintenance, assembly, and repair support.