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C5505 schematics, power pins wiring questions

Mato Hattori
Prodigy 150 points
Other Parts Discussed in Thread: TMS320VC5505, TMS320C5515, TMS320C5505

Hello,

I'm currently drawing schematics using TMS320C5505AZCH chip, and need a help to get clear on how to wire the chip.

1. Reserved pins#J10 & J11
    According to the datasheets,  pin#J10 RSV1 and pin#J11 RSV2 must be tied directly to CVdd, i.e. 1.3V or 1.05V.  
Both C5505 and VC5505 datasheets have same descriptions.
(  VC5505 datasheets = SPRS503B–JUNE 2009–REVISED JANUARY 2010
   C5505 datasheets   = SPRS660D–AUGUST 2010–REVISED APRIL 2011   )
However, looking at the schematics of Spectrum Digital TMS320VC5505 eZDSP USB Stick, pin#J10 and pin#J11 are left unconnected.
Which of these is correct?

 2. pin#A12 ANA_LDOO
    According to the datasheets, pin#A12 ANA_LDOO can be connected to pin#C10 Vdda_pll and pin#A10 Vdda_ana.
As the design is very power conscious, I just don't want to use the series regulator but wish to use an 1.3V switching regulator which is needed also for CVdd.
Can I just connect pin#C10 Vdda_pll and pin#A10 Vdda_ana directly to CVdd, and leave pin#A12 ANA_LDOO unconnected?
If ANA_LDOO is not used, then can I just leave pin#B12 ANA_LDOI also unconnected?

Your help are most appreciated.
Thank you.

 

  • 0
    TI__Mastermind 23785 points

    Hello,

    TMS320C5505 is a bit different than VC5505. But is in the same family as TMS320C5515.

    You have to connect J10 & J11 to CVdd. If you refer to Spectrum Digital's TMS320C5515 EVM and TMS320C5515 EZDSP schematics, they are connected to CVdd.

    You can not leave ANA_LDOI as unconnected because it is also provide power to some input pins and others. Please refer to Table 3-19 of data sheet for reference.

    Regards.

  • 0 in reply to Steve Tsang
    Prodigy 150 points

    Steve,

    Thank you for your clarification.
    I appreciate it.

    As I studied C5505 datasheets and C5515 EzDsp schematics, another questions came up.

    According to TMS320C5505 Datasheet page 43 Table 3-19, pin#12 DSP_LDO_EN# should be enabled (=tied to ground) only to allow RTC only mode.

    As discussed in other thread of this forum, the DSP cannot generate wakeup signal by itself once entered into RTC only mode.
    So, I think it is fair to say that RTC only mode is not really useful to save power consumption of DSP without adding parts around the DSP chip.
    ( it requires external circuit to count timing byitself, maybe a free running multivibrator or sort, to generate wakeup signal. 
      DSP is not allowed to enter RTC only mode and come back byitself just to take a few naps during low load like a sleep mode.  )
    Rather, I believe RTC only mode is intended to allow battery backup of RTC registers while DSP is powered down.

    Then, my simple question is whether I can disable DSP_LDO by pulling high pin#12 DSP_LDO_EN# if folloing two conditions are met;
    1. RTC only mode is not used, i.e. RTC registers are all cleared everytime DSP is powered up. ( RTC will be no longer a Real Time, actually, so it maybe a loss of resource )
    2. RESET signal is provided externally.

    I look forward to hearing from you again.

     

     

  • 0 in reply to Mato Hattori
    TI__Mastermind 23785 points

    Yes. Please refer to Table 4-5 in the data manual to pull DSP_LDO_EN high via LDOI.

    regards.