Using Differential Pairs in Allegro PCB Editor
February 9, 2012 10 Product Version 16.5
Driver-Receiver path, a new Dynamic Phase check was introduced in SPB 16.3 that
performs phase checks at bend point intervals across the differential pair.
The Dynamic Phase check is designed to meet the guidelines suggesting that the path
lengths of the true and complement signals within the differential pair must differ by no
more than "x mils" along the entire path of the net. If at any point on the net, the skew
between true and complement exceeds "x mils", the mismatch needs to be
compensated within "y mils". Representative values for x and y might be x = 20 and y =
600.
The constraints associated with Differential Pairs now support Static and Dynamic Phase.
The margins of each constraint can be set independently using length or time. The
Max_Length (running skew) constraint for Dynamic Phase is limited to length only.
Static Phase Tolerance - A onetime check from Driver to Receiver for comparing lengths
or delay of each member. If a Driver cannot be determined, the check is performed across
the longest path of the pair. (No change in behavior in 16.3)
