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Re: 4 inch-trace between LPDDR memory and DM3730

Bill Liu
Prodigy 30 points
Other Parts Discussed in Thread: DM3730

Hello,

In my design, there are some switches between the LPDDR memory chip and DM3730. The trace length ends up to be 3.5 ~ 4 inches and lumped capacitance ~11pF. Will this be OK with programming Drive Strength to proper level  (Full, three-quarter, half)? I can add series termination resistor to make impedance match. My concern is: the output impedance of the devices (memory and DM) is not constant. It changes with output voltage as well as process and temperature. So perfect impedance match is not possible. There will be some overshoot and undershoot.

By the way, the memory chip to be used is MT46H128M16LFCK (60-ball).

Thanks a lot!

--Bill

  • 0
    TI__Guru* 84110 points

    Bill,

    You must meet the layout, placement, routing, and other design rules as specified in the datasheet. TIs methodology is to support this set of rules. Any design that does not meet these rules is not supported by TI.

    Table 6-16 lists maximum distances, which you are violating.

    Adding switches in series with the LPDDR interface is not supported by TI.

    Regards,
    RandyP

     

    If you need more help, please reply back. If this answers the question, please click  Verify Answer  , below.