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Bypass Capacitors for AM335x in low temperature

takeshi matsuzaki
Expert 2030 points

Hello,

I have a quiestion about AM335x DDR3 Bulk Bypass Capacitors.
Seeing the Datasheet(SPRS717H) P179 "Table 7-62. Bulk Bypass Capacitors",
it needs more than 20uF for AM335x VDDS_DDR bulk bypass total capacitance.

As you know the ceramic capaciotrs have "B characterristics" generally.
www.tdk.co.jp/.../aaa60508.pdf
So if I use AM335x(industrial) in -35°C air, capaciotr's capacitance will downs about -15%.

Does the Datasheet(SPRS717H) say we need 20uF capacitance even in -35°C ?

Regards,
Takeshi Matsuzaki

  • 0
    TI__Guru 62875 points
    The capacitance values provided in the data sheet do not represent an absolute requirement. They provide a good starting point for your design. As you may know, specific characteristics of the decoupling capacitors and how they are connected in the PCB design can influence the Power Distribution Network (PDN) performance more than the actual capacitance values.

    The best way to insure your PDN will perform as expected is by performing a PDN analysis using a model of your specific PCB design. However, we find many customers do not have the tools for modeling their PDN. In many of these cases, they build a prototype using our recommended values and validate their design using the prototype.

    Regards,
    Paul
  • 0 in reply to peaves
    Expert 2030 points

    Hi Paul,

    Thank you for details.
    I undetstood we need a validation to find a good capacitance value.

    Regards,
    Takeshi Matsuzaki