An xSignal is a designer-defined signal path between two nodes. These can be nodes in the same net or, if a series termination component is involved, two nodes within associated nets.
To quickly create an xSignal, select the required start pad and end pad (these can be pads on a component or in Nets mode of the PCB panel) then run the Design >> xSignals sub-menu from the main menus.
1. Designing a PCB
A PCB design is a multi-step process, from creating a schematic block diagram to laying out the board with traces. The design for manufacturing (DFM) requirements of your manufacturer must be accounted for, including component clearance and compliance with design rules.
Once the parts and net connections are organized on the schematic, the designer can begin constructing the layout with a CAD tool. This will involve converting the rubber-band net connections into drawn traces and planes. A number of aids are available to help with this, from design grids to routing features that can keep distinct nets from overlapping.
Another crucial step is designing power and ground planes. These large areas of copper on the board serve to distribute power and ground signals, reducing voltage drops and impedance while improving signal integrity. They can also shield sensitive signals from electromagnetic interference and dissipate heat generated by components. A careful design of these planes will improve the performance of the circuit board.
2. Designing a Printed Circuit Board
Designing a PCB is an important process that involves many different factors. These include material and component selection, layout planning, and mechanical constraints. These factors are important because they affect the function of the finished board. For example, it is necessary to choose materials and components that can withstand the rigors of the circuit board.
Once the schematic has been optimized, it’s time to lay out the traces. This process converts rubber-band net connections into drawn traces and planes using CAD tools. During this phase, the designer must account for physical limitations like space and weight as well as signal integrity issues, such as crosstalk and electromagnetic interference (EMI).
Another consideration is heat dissipation. This can be achieved by implementing thermal relief patterns on through-hole components or by using heat sinks on surface mount parts. It is also important to consider thermal management around critical components that generate a lot of heat. This can be done by placing them near heat sinks or by utilizing thermal vias and pads.
3. Designing a PCB with Xsignal
The xsignal businessfeature in Altium Designer is an extended signal mode that allows multiple nets to be treated as a single signal for the purposes of length matching. In the simplest of cases, a net that starts on one IC pin, terminates on a series termination resistor and continues to another IC pin can be treated as an xSignal.
The PCB panel has a region that displays any xSignal classes that have been defined in your design (All xSignals). The right-click context menu lets you add a class to this list or remove a class from it.
The panel also has a From-To mode. This lets you create From-Tos in a net based on its topology or the arrangement of its nodes. From-Tos can be created either by clicking the Generate button to create them based on your topology, or by selecting two pads in the net and clicking the Add From To button. These From-Tos can then be used in a variety of design tasks, including interactive length tuning.
4. Designing a PCB with Xsignal Lite
A xSignal is a designer-defined signal path between two nodes; these can be nodes within the same net, or nodes in associated nets separated by a component. An xSignal can be used to scope relevant design rules such as Length and Matched Length, which are then obeyed during design tasks, including interactive length tuning.
xSignals are displayed in the panel region as pads joined together by a thin line that represents the path of the signal. The xSignal pad color background indicates the xSignal class (as defined in the xSignals panel region); a right-click context menu offers options to remove an xSignal and change its visual representation in the PCB design space.
In the xSignals panel, select an xSignal class and create an xSignal by clicking the Create xSignal command. When the xSignal is created, select it in the panel to display its xSignal class, node count, and other information in the xSignals region of the dialog.