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Forums > Silicon-package-board > PCB Design

Subject: Cross talk analysis
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mp_ponraj
Posts: 6
Online: User is Offline
3/02/2008 10:39 PM  
Hi,

Can anybody explain how to run Cross talk analysis using specctra?


Thanks in advance.
CSB
Posts: 1
Online: User is Offline
3/04/2008 9:15 PM  
Ponraj

You cannot run Cross talk analysis using specctra. specctra is auto router.

You can set spacing rules to reduce cross talk in specctra.

Regards
Saravana
rb
Posts: 53
Online: User is Offline
3/05/2008 8:28 AM  
Actually the crosstalk checking capabilities in Specctra are quite significant. You can drive the crosstalk rules in Specctra from setting them up in Allegro Constraint Manager or you can set them up directly in Specctra with .do files. Specctra has the capability for both segment length based as well as max-noise based crosstalk control. Shown below are examples of do files for both segment and noise based rules.


rule pcb (max_noise 45)
# Parallel Noise
rule pcb (parallel_noise (gap 0.005) (threshold 0.20) (weight 80.429))
rule pcb (parallel_noise (gap 0.006) (threshold 0.20) (weight 77.177))
rule pcb (parallel_noise (gap 0.007) (threshold 0.20) (weight 50.780))
rule pcb (parallel_noise (gap 0.008) (threshold 0.20) (weight 36.034))
rule pcb (parallel_noise (gap 0.009) (threshold 0.20) (weight 25.655))
rule pcb (parallel_noise (gap 0.010) (threshold 0.20) (weight 25.133))
rule pcb (parallel_noise (gap 0.011) (threshold 0.20) (weight 24.790))
# Tandem Noise
rule pcb (tandem_noise (gap 0.000) (threshold 0.20) (weight 175.309))
rule pcb (tandem_noise (gap 0.001) (threshold 0.20) (weight 141.568))
rule pcb (tandem_noise (gap 0.002) (threshold 0.20) (weight 118.555))
rule pcb (tandem_noise (gap 0.003) (threshold 0.20) (weight 85.537))
rule pcb (tandem_noise (gap 0.004) (threshold 0.20) (weight 59.899))
rule pcb (tandem_noise (gap 0.005) (threshold 0.20) (weight 52.741))
rule pcb (tandem_noise (gap 0.006) (threshold 0.20) (weight 46.994))
rule pcb (tandem_noise (gap 0.007) (threshold 0.20) (weight 42.053))
rule pcb (tandem_noise (gap 0.008) (threshold 0.20) (weight 37.629))
rule pcb (tandem_noise (gap 0.009) (threshold 0.20) (weight 33.849))
===============================================
#General pcb rules
rule pcb (parallel_segment (gap 0.005) (limit 2.349))
rule pcb (parallel_segment (gap 0.006) (limit 3.863))
rule pcb (parallel_segment (gap 0.007) (limit 5.152))
rule pcb (parallel_segment (gap 0.008) (limit 7.886))
rule pcb (parallel_segment (gap 0.009) (limit 12.314))
rule pcb (parallel_segment (gap 0.010) (limit 16.028))
rule pcb (parallel_segment (gap 0.011) (limit 20.225))
# Tandem Crosstalk
rule pcb (tandem_segment (gap 0.000) (limit 2.190))
rule pcb (tandem_segment (gap 0.001) (limit 3.730))
rule pcb (tandem_segment (gap 0.002) (limit 5.350))
rule pcb (tandem_segment (gap 0.003) (limit 7.203))
rule pcb (tandem_segment (gap 0.004) (limit 8.575))
rule pcb (tandem_segment (gap 0.005) (limit 11.203))
rule pcb (tandem_segment (gap 0.006) (limit 14.572))
rule pcb (tandem_segment (gap 0.007) (limit 18.000))
rule pcb (tandem_segment (gap 0.008) (limit 20.000))

The do file examples I have shown above are defined at the PCB PCB level. You can also define class and net level crosstalk rules.

You can apply the crosstalk rules in Specctra to be in place while auto-routing or just apply them after the routing is complete to do post route crosstalk analysis and manual route cleanup. However if they are applied while autorouting it most likely will negativily affect route completion and routing time.

I suggest that you review the Specctra online documentation for crosstalk setup. There is far too much detail for me to cover it in any further depth in this forum.

Randy
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Forums > Silicon-package-board > PCB Design > Cross talk analysis


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