What's Good About Differential Pair Support in PCB Librarian?

2 Oct 2008 • 1 minute read

You may recall a post I made a couple months ago about What's Good About Differential Pair Support in ASA?

In order to establish Differential Pair support for Design Entry HDL (DEHDL), the SPB16.01 release included enhancements to PCB Librarian which allow designers to define diff pair pins.

With the increased signal speeds of complex designs, differential pair signals are becoming more and more prevalent. In order to further reduce the design cycle times using DEHDL as the design capture tool, differential pairs must be taken into consideration. In most situations a differential pair signal connects to two pins of every component on the net.

Some key features for diff pair support in PCB Librarian:

The Differential Pair property is always associated with the Logical Pins of the component/part.
The positive and negative pins comprising the same diff pair will be of the same Pin Type.
You cannot associate a Differential Pair property to the pin types GROUND, POWER or NC.
The Differential Pair property is stored in the chips view of the component/part.

There's a new right mouse button (RMB) menu option which allows you to select the constituent pins in the logical pin grid and then right-click on the selection and choose Create Differential Pair. Choose Global to create differential pairs in all packages or local to create a differential pair in the selected package. You can also remove differential pairs using the same RMB option.

Also, you can add differential pair properties to all parts in a library by executing the con2con command from the command prompt using the -autocreatediffpair option.

Part Developer uses the Default_Diffpair_Value definition in cds.cpm to name differential pairs.
By default, the Default_Diffpair_Value definition is the following:

Default_Diffpair_Value ‘DP_:Prefix’

You can configure the Default_Diffpair_Value definition in your local or site cpm file. For more details about how to define diff pairs in Part Developer, you can consult the Cadence Help documentation or feel free to contact me.

I'm curious how many designers/librarians are taking advantage of this capability in the SPB16.01 release?

As always, I look forward to your feedback!

Jerry GenPart