i.MX 8M Plus DDR4-3200 length matching recommendations

[yamamo10]

I am designing the DDR4 interface for i.MX 8M Plus
(Part Number: MIMX8ML8CVNKZAB) and would like to confirm the
length matching recommendations for DDR4-3200 operation.

In the available documents (IMX8MPHDG, AN5097, etc.),
general guidelines for DDR routing are described.
However, I could not find clear numerical limits for
length matching specifically for DDR4 operation at 3200 MT/s.

For DDR4 running at 3200 MT/s, could you please advise the
recommended length matching (maximum skew / length difference)
for the following signal groups?

- CK (CK/CK#)
- DQS (DQS/DQS#, within a byte lane and between byte lanes)
- DQ (within a byte lane and relative to DQS)
- CA / Address / Control signals

Additionally, could you please clarify:
- Which document should take precedence for length matching rules
on i.MX 8M Plus DDR4 designs
- How much skew can typically be compensated by the internal
DDR training of the SoC

[Rita_Wang]

Please refer to our i.MX 8M Plus Hardware Developer’s Guide and reference board design.

[yamamo10]

Thank you for your previous response.

I understand that the i.MX 8M Plus reference board
does not implement DDR4, and that no explicit DDR4
length-matching values are published.

For DDR4 operation at 3200 MT/s on i.MX 8M Plus,
could you please clarify the recommended design approach
for PCB routing and length matching?

Specifically:
- Is DDR4-3200 operation assumed and validated by design
(with appropriate board design)?
- In the absence of a DDR4 reference board,
what should be considered the primary guideline
for length matching and skew control?

Can AN5097 be used as a general DDR4 routing guideline
for i.MX 8M Plus designs, even though it is not
device-specific, provided that standard DDR4
signal integrity rules are followed?

[Rita_Wang]

For DDR4 operation at 3200 MT/s on i.MX 8M Plus,
could you please clarify the recommended design approach
for PCB routing and length matching?

Specifically:
- Is DDR4-3200 operation assumed and validated by design
(with appropriate board design)?
- In the absence of a DDR4 reference board,
what should be considered the primary guideline
for length matching and skew control?

A: We only supply the hardware guide for the i.MX8MP, for the hardware design using the DDR4 please refer to it. And for the i.MX8MP using the DDR4, we have the validation board design, I will share it to you.

Can AN5097 be used as a general DDR4 routing guideline
for i.MX 8M Plus designs, even though it is not
device-specific, provided that standard DDR4
signal integrity rules are followed?

A:No, do not refer to it, for the i.MX8MP please following the hardware guide for it special.

[yamamo10]

We understand that the hardware guide and the validation board design are the primary references for DDR4 on i.MX 8M Plus.
However, our understanding is that these documents do not sufficiently describe the DDR4 routing, length matching, and skew constraints in detail.

Could you please share the links to the specific hardware guide and the DDR4 validation board design you mentioned, so that we can reconfirm whether we are referencing the correct documents?

[Rita_Wang]

I email to you, please check it.

[yamamo10]

Thank you for sharing the available hardware guide and the validation board design.

We understand that, at this time, there are no additional documents or device-specific guidelines that describe DDR4 PCB routing, length matching, or skew constraints for i.MX 8M Plus beyond the provided materials.

Based on this, we will proceed with our design using general DDR4 signal integrity best practices and internal SI analysis, while following the i.MX8MP hardware guide as the primary reference.

Thank you for your support.

If any additional recommendations or updates become available in the future, we would appreciate your sharing them.

[Rita_Wang]

Dear @yamamo10 ,

I do not have and found the special document for the DDR4, I will still continue checking it for you, when I have update information I will share to you.

I remmber your needs.

Wish you have a nice day and weekend

Wish you have a nice day

Best Regards

Rita