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Original question:

Is VTT Termination required for DDR_CKE

AM3352: Pull down DDR_CKE to enable sleep feature

Tony Tang
Mastermind 28032 points
Part Number: AM3352

In datasheet Figure 7-49, the DDR_CKE is pulled up to DDR_VTT. if so the device can't wake up after sleep. I checked over the forum and hardware checklist, it is recommended to pull down DDR_CKE. so the datasheet is conflicted with real case. how about to update the datasheet?

  • 0
    TI__Guru* 80020 points

    For designs which do not employ low power deep sleep, CKE can be terminated to VTT as shown in the datasheet diagram.  If your design will be utilizing low power deep sleep, the CKE signal should not be terminated to VTT, and should be pulled low to help maintain its state during deep sleep mode.

    Regards,

    James

  • 0 in reply to JJD
    TI__Mastermind 28032 points

    Thanks James,

    Since both pull down and pull up works, and pull down can work with low power deep sleep mode, why not only recommend pull down in datasheet.

    And what is the benefit of pull up DDR_CKE?

  • +1 in reply to Tony Tang
    TI__Guru* 80020 points

    Tony, the connection to VTT is not technically a pullup, it is a termination to VTT voltage, which is the recommended termination for all addr/ctrl signals in a fly-by topology.  For low power designs, we have to break that recommendation and pull CKE low

    Regards,

    James