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Is VTT Termination required for DDR_CKE

Sandeep Yadav
Prodigy 60 points
Other Parts Discussed in Thread: TPS51200

Hi,

I am using AM335X processor and want to interface an DDR3 to it. Is it required to provide VTT termination for DDR_CKE.

  • 0
    TI__Guru**** 161600 points
    Hi Sandeep,
    Check the AM335x Schematic Checklist: processors.wiki.ti.com/.../AM335x_Schematic_Checklist
    "DDR3
    -- be sure to include a termination regulator for properly terminating the clock/control signals. Check datasheet and/or reference schematic for proper connection. Recommend TPS51200
    -- do not connect DDR_RESET or DDR_CKE to VTT termination resistors. These should be connected directly between AM335x and DDR.
    -- check datasheet for proper termination voltages. Termination for clock signals is VDDS_DDR (along with an AC coupling capacitor), whereas all other signals need to use VTT for the termination voltage. Check the datasheet for details.
    -- If not using VTT, VREF should obtained using a resistor divider (10Kohm 1%) with capacitive decoupling to ground, and should be used as references for both CA and DQ pins on the memory, as well as the VREF signal on AM335x. Ensure resistor is a high precision (1%) resistor as specified in the datasheet. When not using VTT, be sure especially follow the routing guidelines in the datasheet."

    Best Regards,
    Yordan