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AM5718: DDR ball state

yf liao
Expert 1080 points

Part Number: AM5718
Other Parts Discussed in Thread: AM5728

Hi, I just realized that there are a couple of DDR signals have different ball reset state and reset release state between AM5718 and AM5728. For example, ddr1_cke on AM5718 is PU, drive 1 vs AM5728 PD , drive 0.

Will those different ball state impact the DDR circuit design which aims at a compatible design between the AM5728 and AM5718?

Another question on signal ddr_cke, there is 4.7KOHM pull down resistor on AM5728 GP EVM, but not on AM5718 IDK EVM, does this resistor a must for AM5718 as well?

  • 0
    TI__Guru**** 393215 points

    Hi,

    You should note that the internal pulls are active only when the device is in Reset state. At reset release time the pulls are turned OFF. However it's true that the 2 devices drive different levels on CKE. This will not impact design compatibility, as the EMIF is not initialized at that time. regarding the external pulldown, my advice is to place it on a custom board. Its function is to pull CKE low when the processor enters low-power modes, and the DDR is placed in self-refresh.