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AM5746: DDR3 VTT Termination in IDK Schematic

Kanae
Guru 10245 points

Part Number: AM5746

Hi Team,


Regarding the following marked area of TMDSIDK574 Schematic Sheet 10,
my customer has the following questions.


-Q1. Purpose and application of capacitors

-Number of capacitors required
　　Q2: Is it correct to assume that the required quantity differs for each artwork?
　　Q3: What is the recommended number of capacitors for the initial design?

-Condenser placement when designing artwork
　　Q4: Where is the optimal mounting position? Please let us know the mounting position.
　　Q5: When describing a capacitor in a circuit diagram,
             should it be placed near the termination section, as shown in the circuit diagram above?

Best Regards,
Kanae

  • +1
    TI__Guru 55715 points

    The VTT regulator can both source and sink current.  The purpose of the VTT termination decoupling capacitors is to minimize the amount of noise on termination supply (VTT) by providing optimum path for return currents.  Yes - the specific number of capacitors may vary with different design, the EVM reference is a good starting point.  The DDR3 signals are routed in daisy-chain fashion - source to load to load to termination resistor.  Typically a VTT plane segment is created for the termination resistors, and the plane segment has several decoupling capacitors to service all signals.  

  • 0 in reply to Robert Eschler
    Guru 10245 points

    Hi Robert,

    Thank you for your support.
    I have no additional questions from my customer,
    so I will close this thread.

    Best regards,
    Kanae