BoardSurfers: Training Insights: Setting Up and Using Pin Delays in Constraint Manager

Pin delays are used to specify the time delay or length from the internal package connection to the pin’s mounting layer. It is critical to include pin delays when tuning high-speed nets to ensure signal performance. Pin delays are used in the calculation of electrical checks, such as differential pair phase tolerance, propagation delay, and relative propagation delay. Allegro^® Constraint Manager allows you to specify pin delays at schematic or board-level, by associating the Pin Delay property with a particular component instance pins. This property manages inter-chip delay or die-to-die timing paths across a board and thereby factor inter-package delay into timing requirements.

In this blog post, you will see how to enable pin delay constraints for the calculation of relative propagation delays.

Setting Up Pin Delay in Allegro Constraint Manager

You can specify pin delay constraints in Allegro Constraint Manager. Choose Electrical ─ Net ─ Routing ─ Relative Propagation Delay worksheet. The Pin Delay column is next to the Pin Pairs column. In case you do not find the Pin Delay column, choose View ─ Show all columns.

To perform pin delay calculations, you must first enable the pin delay checks in the Analysis Modes dialog. Choose Analyze ─ Analysis modes and open the Electrical checks. Under the Electrical Options, you will find the Pin Delay section. Enable the Include in all Propagation Delays in Differential Pair phase checks checkbox. This option includes min/max/relative propagation delays and differential pair phase tolerance constraint checks.

Pin delay constraints can be specified either using a unit of time or length. If you specify the pin delay in units of length you need not worry about setting the value of the Propagation Velocity Factor. Click OK to close the Analysis Modes dialog.

Enter the delay values for pins in the Relative Propagation Delay worksheet and get the propagation delay values calculated. You can now analyze your match groups with pin delay values. An example of pin delay usage for calculating the length of traces in a match group is best illustrated in the following video link.

To learn in detail about this flow, watch the How to Set Up and Use Pin Delays from within the Constraint Manager training byte on the Cadence^® Support portal. Click the training byte link now or visit Cadence Support and search for this training byte under Video Library.

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