AM3352: Datasheet question about DDR3

Hiroyasu Tazawa1

Guru 12350 points

Part Number: AM3352

Hi, Everyone

I have a qustion about Datasheet of AM335x for DDR3.

It is described in Table 7-66 of Datasheet below

Can you explain about No.17 "CK center-to-center spacing" ?
Is it space between CK and CKn ?
and Why it is empty ?

Best Regards
Hiroyasu

over 8 years ago

0 peaves over 8 years ago

TI__Guru 62855 points

This parameter is a function of your PCB design. The spacing of the two signals that make up the differential clock must be adjusted to prove the proper differential impedance. The attached note #12 explains the requirement.

Regards,
Paul

0 Hiroyasu Tazawa1 over 8 years ago in reply to peaves

Guru 12350 points

Hi, Paul

Thank you for your reply.
I got it, but I do not understnad why it is empty.
Can you tell me this reason ?

Best Regards
Hiroyasu

0 peaves over 8 years ago in reply to Hiroyasu Tazawa1

TI__Guru 62855 points

The impedance of a differential signal trace is a function of trace widths of each signal, spacing between the two signals, distance above the reference plane, and dielectric constant of the PCB board materials. Therefore, this spacing must be determined by working with your PCB designer and fabrication vendor during PCB design. We list this parameter in the table as a reminder for you to check when designing the PCB.

Regards,
Paul

0 Hiroyasu Tazawa1 over 8 years ago in reply to peaves

Guru 12350 points

Hi, Paul

Thank you !
I got it.

Best Regards
Hiroyasu

0 Hiroyasu Tazawa1 over 8 years ago in reply to peaves

Guru 12350 points

Hi, Paul

Sorry. I have another question.

Can you tell me what difference No14 and No18 ?

NO.14　Center-to-center CK to other DDR3 trace spacing
NO.18　CK spacing to other net

Best Regards
Hiroyasu

0 peaves over 8 years ago in reply to Hiroyasu Tazawa1

TI__Guru 62855 points

NO.14 is the center to center distance from the clock signal to any other DDR signal.
NO.18 is the center to center distance from the clock signal to any non-DDR related signal on the PCB.

Regards,
Paul

0 Hiroyasu Tazawa1 over 8 years ago in reply to peaves

Guru 12350 points

Hi, Paul

Thank you.
I got it.

Best Regards
Hiroyasu

Processors

Processors forum

AM3352: Datasheet question about DDR3