Hi Forum,
I am currently working on a design where I need to route a differential pair to two SMA connectors seperated by 20 mm. please see the attached picture for your reference. when i select the route differential pair nets the trace wont complete. any suggestions are welcome.
Regards,
-AP
A few quick things to check:
Make sure your differential nets names are labeled correctly. Like “SMA1+” and “SMA1-”. The names must be identical with a “+” and “-” at the end.
Double check your PCB and differential routing design rules. It’s possible a PCB design rule sets a clearance larger than your differential routing gap rules, in which case it will not route.
Your SMA connectors look really far apart for the tool to pick them up as a differential route. You may have to route the legs out of the connectors manually to the center, being careful to keep them mirrored, then complete the routing with the the differential tool from the center meeting point.
Is it really 200 mm ?
BTW if the track lengths are an important matter, you can use the appropriate tool to tweak them (Route/ Tune track length).
Thanks to your suggestions I wil retry
Err its a typo 20mm sorry about that
Having tried really hard the draw differential pair now completes the pair net. but its still not as good as what it is on the image provided above. I am attaching my project for your reference. I would appreciate any help.
kicad_diff_pair.zip (12.0 KB)
The router can’t handle such unusual situations, like the diff pair being split into two single-ended tracks going to connectors spaced apart by 20 mm. Try routing the diff pair using the diff pair tool as far as it’s still coupled and then route both traces leading to the SMA connectors using ‘place track tool’.
Tom
then how would i make sure my impedance is 100 ohm and how to match trace lengths are equal ?
How do you plan to have 100 ohm diff impedance in the part where the diff pair splits into two separate traces each going to a separate SMA connector?
T.
I do not how know how i will do that. as suggested by you in the previous comment i will try to place differential pair as far as i can and then try to place single ended trace to the remaining distance. I will try to send the design to the chip vendor to see if he approves of this. this is the first time i am entering the domain of high speed design so i have no clue if what i am doing is right or wrong.
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