66AK2G12: MMC trace for uSD card

Brian Antheunisse

Part Number: 66AK2G12

Team,

From my customer:

Our board has K2G MMC0 interface connected to uSD connector. We followed the sprac54a, 66AK2Gx Schematic Checklist, and the our board is working. In the future, we might change the board size and I would like to know K2G MMC0 layout guidelines.

Is there any requirement on MMC trace (for uSD card), e.g. length matching? I couldn’t find it in Wiki or datasheet. Thanks.

Thanks,

Brian

over 5 years ago

0 Yordan Kovachev over 5 years ago

TI__Guru**** 161600 points

Hi Brian,

How much is the planned increase in the board size?
I found some old application report for OMAP4, which states that you shouldn't exceed 10 cm trace length for the MMC traces:
www.ti.com/.../swpa221.pdf
which seems a valid value. As far as I know having traces longer than 10 cm may cause problems.

Best Regards,
Yordan

0 Brian Antheunisse over 5 years ago in reply to Yordan Kovachev

TI__Expert 5215 points

Yordan,

By looking at K2G EVM board, the MMC0 trace lengths are longer than 12cm.

Actually, they are thinking to reduce their board size. The trace routing will change. We would like to know the limits of length skews among MMC0_CLK, MMC0_CMD, and MMC0_DATA0 ~ 3.

Any chance we can get Bill T. to make a comment since he designed the EVM?

Thanks,

Brian

0 Bill Taboada over 5 years ago in reply to Brian Antheunisse

TI__Mastermind 42545 points

Hi Brian,
We went a little long on the SD card interface on the K2G. 10 cm is a good limit for that interface. The max clock speed is 25MHz so the length matching isn't too strict. All data lines should be with 500mil difference in length from the clock.
Regards, Bill

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66AK2G12: MMC trace for uSD card