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Decoupling Cap for C5505 DV_DDEMIF

_mk
Expert 4565 points

Hi,

I have a customer with a C5505 device and is GPIO[21-26] pins instead of using the EMIF pins within the submodule. Still these pins are supplied from DV_DDEMIF. The customer is looking at reference designs with 9 .1uF (one per supply pin) and a 10uF bulk cap.

I've looked through the data sheet and at the processor wiki site about BGA decoupling [1] and can't find anything other than general guidelines. The customer is not using EMIF (which is being used in his reference design) and wants to know if he can remove some of the caps because he is only supplying 6 GPIO pins. I've also communicated that if he can use other GPIO pins he doesn't need to even use the EMIF module but he does not have any spare GPIO pins.

Can anyone give me more specific information about a possible minimum number of caps for the EMIF submodule?

Thanks,

Matt

[1]http://processors.wiki.ti.com/index.php/General_hardware_design/BGA_PCB_design/BGA_decoupling#Value_For_Pin_Capacitors

  • 0
    TI__Mastermind 23785 points

    Matt,

    I believe the 10uF bulk cap is fine, but not sure about the 9.1uF. If you refer to the C5515 EVM schematic, there is a 10uF and an array of 0.1uf for low/high frequency noise. The number of caps depends on individual board layout  and operational frequency.

    Hope this help.

    Regards.

  • 0 in reply to Steve Tsang
    TI__Expert 4565 points

    Hey Steve,


    Thanks for the quick response. This is the current reference design they are using so worst-case they can use the same caps to be safe. They are wanting to know if they can reduce the number of caps from this design. Do you know of a reference design that uses the EMIF pins as GPIO instead that I may be able to compare against?

    According to the general guidelines in the TI wiki link in the first post they would be able to use 5 .1uF and 1 15uF due to the 9 supply pins for the EMIF module. Just wondering if there are resources that give specific information on how to calculate this instead of just general guidelines.

    Thanks for your help!

    Matt

  • 0 in reply to _mk
    TI__Mastermind 23785 points

    Matt,

    I am not aware of any design using as GPIO only. C5505 ezDSP and C5515 EVM both supports EMIF.  C5535 does not support EMIF but GPIO[21:26] also not supported. The DVDDEMIF is grounded.

    Regards.