AM1808 DDR2: termination <==> weak drive

Thomas Wappler

Other Parts Discussed in Thread: AM1808

Hi,

I have two boards using the AM1808 (one ZWT, one ZCE) and both with micron MT47H64M16HR-25E.

Both boards do not use serial terminiation, therfore the memory was programmed to weak drive as the datasheets says: "When no termination is used on data lines (0 Ω), the DDR2/mDDR devices must be programmed to operate in 60% strength mode."

Both boards show memory errors when using weak drive, but work fine with normal drive.

Is it allowed to use normal drive even without serial termination (it's written "_MUST_ be programmed"...)?

Can anyone think of an reason?

Thanks,

Thomas.

over 13 years ago

0 jc-ti over 13 years ago

TI__Mastermind 27585 points

Can you give the entire part number for the memory, ie MT47H64M16HR-25E:H or MT47H64M16HR-25E:G?

It should work in weak drive strength mode given that the routing layout rules were followed. Have you confirmed that it complies with the datasheet routing spec?

Jeff

0 Thomas Wappler over 13 years ago in reply to jc-ti

Intellectual 395 points

Hi Jeff,

the part number of the memory is MT47H64M16HR-25E IT:H.

I've checked the my board (the ZCE one) against the rules. I did'nt check the other one by myself, but I have a passed report.

The boards where designed by different people with different software. I know that this is no guarenty, but I would wonder if there is the same mistake in both designs. If helpful, I could provide the design data of my design.

Thanks,

Thomas.

0 Mukul Bhatnagar over 13 years ago in reply to Thomas Wappler

TI__Guru* 83885 points

Thomas

Do you have a local TI field office supporting this issue?

Regards

Mukul

0 Thomas Wappler over 13 years ago in reply to Mukul Bhatnagar

Intellectual 395 points

Hello Mukul,

yes, Mr. Stapelfeldt is involved in this problem. I think he monitors this thread.

Thanks,

Thomas.

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AM1808 DDR2: termination <==> weak drive