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Original question:

TMS320DM8148: DDR3 Termination Resistor VDDQ_1V5?

TMS320DM8148: TMS320DM8148

Hareesh Panakkal
Prodigy 210 points
Part Number: TMS320DM8148

Hi All, 

From the picture, the capacitor one is end is connected to VDDQ_1V5. Why it is not connected to ground?

  • 0
    TI__Mastermind 46642 points

    Hareesh,

    The CK and address circuits are different.  Whereas CK is 50-Ohm AC coupled to VDD_DDR (not using VTT), ADDR is 50-Ohm DC terminated to VTT.  The caps on address are not really termination; they are for decoupling of the VTT net of the address bus.  Since VTT is a mid-rail net (= VDD_DDR/2), it can be decoupled either to VSS or to VDD_DDR.  

    The approach shown has been fully validated by TI and if you're designing a new system is the recommended approach for DM8148 to interface to DDR.

    Regards,

    Kyle