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DM3730 CUS package and Micron DDR

Pawel Cern
Prodigy 145 points
Other Parts Discussed in Thread: DM3730

Hi,

We have our custom board project, based on the following components:

- DM3730CUSD100 SOC from TI, main oscillator is 38,4MHz (KC2520C38.4000C1LE00)

- TPS65951A12GU PMIC from TI

- MT46H64M32LFCM-6IT LPDDR memory from Micron. Memory clock is 166MHz (DDR333). Capacity 256MB.

Everything works well except SD card interface. Occasional, single bit errors occur. We did the following test in Linux:

# Create random test file

dd if=/dev/urandom of=aaa bs=1048576 count=256

# Copy

cp aaa bbb

# Flush memory caches

echo 3 > /proc/sys/vm/drop_caches

# Compare

cmp aaa bbb

Last two commands executes in loop. And usually cmp says the files are different. Offset of the difference varies. We saw no MMC related error messages in dmesg (actually nothing except system startup messages).

The phenomena appears on most of the boards. Probability of the error depends on the board, but typically is around 1 - 2 bit errors per gigabyte of data transferred. However, other boards (around 20%) work OK. The problem decreases as DDR clock decrease. Disappears below ~ 100MHz (DDR200). We decided to replace memory chip on two "faulty" boards and after that they are OK.The replacement proved the problem has nothing common with SD card interface as we suspected before, but DDR link between DM3730 and memory. At the beginning we suspected our bug in either u-boot or PCB project, but we couldn't find anything wrong. The board meets DDR routing requirements described in DM3730 data manual. And SDRC register settings were calculated using your spreadsheet found on TI E2E:

http://processors.wiki.ti.com/index.php?title=Setting_up_AM37x_SDRC_registers

Finally we got two development kits from Embest - DevKit 8500D. There is DM3730 in CUS package on board. Other components are slightly different, but it doesn't matter. We tried to do exactly the same tests as described above (file copy/compare on SD card), using ORIGINAL MANUFACTURER SOFTWARE DELIVERED ON DVD. And we saw the same phenomena on both. Overtaking your question, we tried to use SD cards from different vendors, but it doesn't change anything.

BeagleBoard (we have 5 pieces) seems not to be affected. However, there is a "burger" architecture, i.e. PoP memory.

Could you please tell me if there are any known interoperatibility issues between DM3730 in CUS package and Micron LPDDR memories? 

  • 0
    TI__Guru 65405 points

    Hi Pawel,

    There are many devices which using DM3730 with PoP memory but such kind of problem is not reported. There is no information about any issues related to DM3730 in CUS package and Micron LPDDR memories described in the Silicon Errata (sprz319f.pdf). I guess that the memory clocked at 166 MHz (DDR333) could cases some issues because according to the DM3730/25 Datasheet (SPRS685D) section 6.4.2.1 LPDDR Interface - The LPDDR interface on the top of the POP package has been designed for compatibility any POP LPDDR device with a matching footprint and compliance with the JEDEC LPDDR-266 specification.

    BR

    Tsvetolin Shulev

  • 0 in reply to Cvetolin Shulev-XID
    Prodigy 145 points

    Hi Tsvetolin,

    Point 6.4.2.1.2 states:

    "Generally, the LPDDR interface is compatible with x16 and x32 LPDDR266 and LPDDR333 speed grade LPDDR devices."

    So I am confused a little. The paragrap doesn't distinguish PoP and CUS packages. U-boot found on denx web site, for BeagleBoard sets up DDR memory as DDR400. It is even more than the paragraph declares, and all BeagleBoards which we have, work well at this rate. Also table 4-22 in the same document states CORE_CLK can be as high as 400MHz (SDRC clock comes from here).

    But never mind... could you clearly state maximum supported LPDDR clock rates for each DM3730 package? That information is not presented in timing tables.

    Paul

  • 0 in reply to Pawel Cern
    Prodigy 145 points

    Hi,


    We did more tests and the situation is as follows:

    1. The problem occurs when Linux is booted from SD card and files for comparison are also on SD card. We have no NAND on board so can't boot from NAND.

    2. We put file comparison on SD card in the background and ran file comparison on USB pen drive (simultaneiusly, two processes). The problem occurs ONLY on SD card. Please have in mind we tried to replace memory component on two boards and it helped.

    Kind regards

    Paul

    By the way, dear readers, if you have evaluation boards or your own boards with DM3730 in CUS package and micro SD card on board - could you please do the same test as described at the beginning of the conversation? 

  • 0 in reply to Pawel Cern
    TI__Guru*** 125430 points

    Pawel Cern said:
    Please have in mind we tried to replace memory component on two boards and it helped.

    I would recommend trying a few more tests.  I would recommend that you try replacing the processor on a few problematic boards and that you try replacing the memory on a few other problematic boards.  If the problem consistently follows the memory then you'll need to discuss with Micron.

  • 0 in reply to Brad Griffis
    Prodigy 145 points

    Hi,

    We replaced DM3730 chip on one board (did one try till now). It reduced error frequency but not eliminated at all. Also we tried to contact with Micron a week ago, but till today there is no response. I would like to ask you for one more thing. There is a statement on Micron web site:

    Q: What Mobile LPDRAM parts have been validated on the OMAP35x?
    A: Micron works closely with Texas Instruments (TI) to validate and optimize our parts for the OMAP35x processors. As we work with the OMAP35x team, the list of validated memory devices expands frequently. For the most current information, contact your local Micron support, or contact Micron Product Sales Support.
    Could you please confirm which of Micron non-PoP memories (Micron or others) are known to be working correctly with DM3730 in CUS package? If there are any, could you please recommend validated evaluation board which:
    a) has DM3730 in CUS package on board
    b) has non-PoP Micron LPDDR memory
    c) has SD / MicroSD card slot
    Kind regards
    Paul
  • 0 in reply to Pawel Cern
    TI__Guru*** 125430 points

    Pawel Cern said:
    Could you please confirm which of Micron non-PoP memories (Micron or others) are known to be working correctly with DM3730 in CUS package?

    By the way, you didn't mention which revision of that particular DRAM you're using.  The revisions relate to the process technologies (50nm, 40nm, etc.).  I have customers on Rev B (aka T79M) of that device that are in mass production with no issues.

    Pawel Cern said:
    If there are any, could you please recommend validated evaluation board which:
    a) has DM3730 in CUS package on board
    b) has non-PoP Micron LPDDR memory
    c) has SD / MicroSD card slot

    There are no boards (at least not from TI) that have the CUS package.

    Pawel Cern said:
    We replaced DM3730 chip on one board (did one try till now). It reduced error frequency but not eliminated at all.

    This finding is consistent in terms of the issue relating to the memory and not to the processor.  You need to take this up with Micron.