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VC5509A Real Time Clock

j-breeze
Mastermind 7560 points

Hi,

Can I use the VC5509A RTC while the rest of the DSP is not powered? If so, is there any minimum voltage spec of  RCVdd and RDVdd?

Thanks in advece for your cooperation.

j-breeze

 

 

  • 0
    TI__Genius 13045 points

    The RTC module has separate clock and power isolated from the rest of the DSP, so it can be used when DSP is powered down.  Details on the RTC module can be found in www-s.ti.com/sc/techlit/SPRU594.

    The requirements for the RTC power are given in the data manual which is available at www-s.ti.com/sc/techlit/SPRS205..  Look at Section 5.2.2.

  • 0 in reply to TommyG
    Mastermind 7560 points

    TommyG-san,

    Thank you for your reply.

    I 've read the documents, however there was no the minimum voltage spec of  RCVdd and RDVdd when DSP is powered "down".

    Could you have any spec information about  RCVdd and RDVdd when DSP is powered down, not powered on?

    Best regards,

     j-breeze

  • 0 in reply to j-breeze
    TI__Genius 13045 points

    The values for RCVdd and RDVdd listed in the Data Manual, Sec 5.2.2, pg 82 are the same whether the DSP is powered or not.  This is because RTC has isolated power supply which is separate from the rest of the DSP as stated in RTC Reference Guide, Sec 1, pg 12.

    Regards,
    TommyG

  • 0 in reply to TommyG
    Mastermind 7560 points

    TommyG-san,
    Thank you for your kindly support.

    I'd like to ask you one more question.
    Is there any use case that TI customer use VC5509A RTC when DSP is powered down?

    If you have any, please let me know.

    Best regards,
     j-breeze

  • 0 in reply to j-breeze
    TI__Genius 13045 points

    j-breeze,

    I do not know personally of customer using RTC when DSP is powered down, but feature was added at customer request.  Earlier devices did not have RTC power isolated from rest of DSP.

    Anyone else out there using RTC with DSP powered down?

     

  • 0 in reply to TommyG
    Mastermind 7560 points

    TommyG-san,
    Thank you for your corperation.

    I'd like to close this topic. I'm considering whether I will recommend to my customer to use the RTC, but I could confirm that the RTC works properly when DSP is powered down by using VC5509A-DSK anyway.

    Thanks again.

    Regards,
    j-breeze

  • 0 in reply to j-breeze
    Prodigy 40 points

    I had a lot of  problems using the RTC. I cant use it.

    The datasheet says that RCVDD and RDVDD is about 1.35v, but the MMB0 use 3.3V.

    What is correct?

  • 0 in reply to Mario Buratto
    TI__Mastermind 23785 points

    Both are correct. C5509A RTC requires 1.35V. The ADS1282EVM is a seperate board requires 3.3V.

    Regards. 

  • 0 in reply to Steve Tsang
    Prodigy 40 points

    I´m confused. The maximum voltage at these pins (RCVDD and RDVDD)  are 1.42V, item 5.2.2 at Electrical Specifications page 82 November 2002 − Revised January 2008 SPRS205K.

    Can i put 3.3V? It will burn the internal circuit, or not?

    My circuit feed these pins with 3.3V like MMB0, but the circuit doesnt work. I checked the clock and it is ok.

    Can you help me?

  • 0 in reply to Mario Buratto
    TI__Mastermind 23785 points

    Yes. You possibly has demaged the chip. It cannot operate with 3.3V. 

    These pins are specified a maximum operating conditions to achieve the maximum operating frequency reliably. Even if you refer to the 200MHz operating condition, the maximum voltage is 1.65V.

    Regards.