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AM3703: MMC issue at low temperature

Part Number: AM3703

Hi team,

Our customer is developing the system with AM3707, customer is verifying μSD-card I/F at this time. Recently, customer noticed some their prototype-system/application was freeze during Read/Write access at low temperature (0 degree Celsius). When Varistor is removed, this freeze issue was resolved. Customer observed SDIO signals, however, there is not any difference. Customer need to know the reason why this issue resolved when Varistor is removed.

I tried to summarize customer’s report( AM3703_SDcard_ReadWrite_Verification_with_Varistor.pptx ). Can we have any Expert’s comments on this, please?

 

Also, when only AM3703 chip was cooled down by something like small ice-pack, it seems AM3703 goes freeze. n this case, this freeze issue also was resolved when Varistor is removed.

Your comment on this would be highly appreciated.

best regards,

Miyazaki

  • I recommend you review the schematic checklist.

     

    http://processors.wiki.ti.com/index.php/AM37x/DM37x_Schematic_Checklist

     

    Based on the scope trace shown in Wave2 on slide # 2 of the PPT, it looks like the interface may have locked during a data transfer. If so, this is not normal behavior. I also see lots of over-shoot and under-shoot on your signals. I do not know if this is a probing issue or real, but may be part of the problem. If real, you need to resolve these signal integrity issues with a better PCB layout.

     

    One thing that may contribute is the lack of a series termination resistor located as close as possible to the AM3703 CLK terminal. Each MMC CLK terminal has an output buffer that sources the clock signal to the attached device. This signal is also looped back into the AM3703 MMC logic via a input buffer connected to the same MMC CLK terminal. A series termination resistor is needed on the source end of the CLK transmission line to prevent signal distortion at the source end of the transmission line from creating an internal clock glitch.

     

    I suspect your design has marginal signal integrity and removing the ESD protection devices improves it just enough to work at colder temperatures.

     

    Regards,

    Paul

  • Hi Paul,

    Thanks for your detail explanation and comments on this.

    I shared them with our customer. I really appreciate your supports

     

    Best regards, Miyazaki