About Center-to-center DQ[x] to other DQ[x] trace spacing of AM335x DDR2 design.

RY9983

Hello.

I have refered AM335x datasheet Table 5-53(sprs717e: P165).
There is a description:
No.8 Center-to-center DQ[x] to other DQ[x] trace spacing .. 3w[MIN]
(3) Center-to-center spacing is allowed to fall to minimum (w) for up to 500 mils of routed length to accommodate BGA escape and routing congestion.

Since the note(3) allows that the routed length is minimum(w) for up to 500 mils, how long routed length is allowed when center-to-center spacing is 2w?

Our important customer would like to know this.
They are thinking that this rule is concern for effect of crosstalk.
In generally, if it will be a wider pattern width, it will be the longer the distance.
Whether this considering is correct, may I have your help?

Best regards, RY

over 12 years ago

0 Biser Gatchev-XID over 12 years ago

TI__Guru**** 393215 points

Hi RY,

Note 3 is an allowed exception. The 3W spacing should be followed throughout the design.

0 RY9983 over 12 years ago in reply to Biser Gatchev-XID

Guru 10570 points

Biser-san.

Thank you very much for your answer.
May I have once more question?

They are thinking that this rule is concern for effect of crosstalk. Is it right?

Best regards, RY

0 Biser Gatchev-XID over 12 years ago in reply to RY9983

TI__Guru**** 393215 points

Yes, this is correct. As a personal opinion, they could go down to 2W for distances longer than 500mils, especially if they are designing for DDR2, as the work frequencies are not too high for AM335X (266MHz for DDR2 and 303MHz for DDR3).

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About Center-to-center DQ[x] to other DQ[x] trace spacing of AM335x DDR2 design.