[PCB_FORUM] Re: [BULK] - Differential Pairs on 15.2

I believe you can do this by defeating the phase tolerance (make it big)
then applying a relative prop delay.

-Bill

? wrote:
> I don't think you can setup an exact difference for a diff pair.
> We use the uncoupled length, Gather control = ignore and then setup max mm 
> and phase tolerance.
> On our chips the the general rule is that the trace should be equal lenght 
> from the BGA edge.
> Another ways is to include the first peace of trace in the connector/chip 
> symbol.
> Finally you can make a clength report including delay and import it into 
> excel to check the lengths
> 
> Hi
> Peter Sørensen
> MTS Engineer
> Ethernet Product Group
> Vitesse Semiconductor Corporation
> Location: Hørkær 16, 2730 Denmark
> Tlf    +45 4485-5996
> Cell  +45 4050-7098
> Fax. +45 4485-5939 
> 
> 
> 
> 
> 
> 
> -----Original Message-----
> From: Musetti, Carl [mailto:cmusetti@xxxxxxxxxxxxxxxx]
> Sent: 8. december 2004 15:48
> To: icu-pcb-forum@xxxxxxxxxxxxx
> Subject: [BULK] - [PCB_FORUM] Differential Pairs on 15.2
> 
> 
> Hi All,
> 
>       Has anyone had to deal with differential pairs in 15.2 that are not 
> balanced out of the IC. The Mellanox
> InfiniHost_III_MT25208 spec that the PCIX bus diff pairs are not balanced out 
> the chip and give the skews and states that the skew must be accounted for on 
> the PC layout to balance the pair completely end to end. How would I 
> configure this rule in allegro? For instance is there a way to tell the tool 
> to route the + end 50 mils longer than - end?
> 
> Thanks for all replies in advance
> 
> Carl
> 
> ************************************************************
> * Carl T. Musetti              Infinicon Systems           *
> * Tel: 610-233-4828            680 American Ave, Suite 100 *
> * Fax: 610-233-4777            King of Prussia, PA 19406   *
> * cmusetti@xxxxxxxxxxxxx                                   *
> ************************************************************
> 
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-- 
Bill Gerner
Voice: (781) 442-2649 x22649
Fax:   (781) 442-1651 x21651
Email: william.gerner@xxxxxxx
Sun Microsystems
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Burlington, MA 01803;MS UBUR02-205

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