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TPS65930 32kHz clock question

Faizul Bacchus
Intellectual 1895 points
Other Parts Discussed in Thread: TPS65930, OMAP3530

Hello,

Our customer has the following question:

"I was looking at the 32.768KHz clock generation circuit on the TPS65930 and noticed in the data manual (page 83) that an external crystal can only be used in master mode; in slave mode the TRM (page 100) says that the internal oscillator circuitry is bypassed and it requires an external signal to be applied.

 Is that correct -  if I configure the device in slave mode I have to use an external oscillator instead of just a crystal?

 If so, why would that be?

 On our prototype board I will have options to boot in either mode, but our production design would not use a power-on button and

so I was planning to use slave mode and kick it off with the 3.3V PG signal.  "

Please comment on question.

Thanks.

  • 0
    TI__Genius 15100 points

    Hi Faizul,

    In slave mode the device requires the following two external connections:

    1. 32K clk and

    2. IO supply

    In slave mode the device behaves as a slave and responds to an external event like the PWRON. The master and slave mode are design specs and the modes are built for different requirements. The user will have to satisfy these conditions for slave mode.

    Let me know if you have any questions.

     

    Regards,

    Gandhar.

     

  • 0 in reply to Gandhar Dighe
    Intellectual 300 points

    Hi Gandhar,

    I am using TPS65930 PMIC to power my OMAP3530 processor. I have configured the PMIC in Master_C021 (MC021) boot mode.

    I am facing the below issue in some of my boards:

    External 32.768-kHz crystal is given for the PMIC. When I power on my board, VIO = 0.6V, VDD1 & VDD2 = 0V. Also there is no output from 32kHz crystal.

    When I touch the crystal, I get proper voltages, i.e., VIO = 1.8V, VDD1 & VDD2 = 1.2V, but still there is no output from 32kHz crystal.

    May I know what may be the issue. Is there any relation between the 32kHz circuitry & other pins of the PMIC.

    Regards,

    Rahul.

     

     

  • 0 in reply to Rahul16136
    TI__Genius 15100 points

    Your board seems to have issues with crystal getting to stabilize the 32K clock. Do yo have the correct load caps. Unless you get a good 32K you may not power up the board properly.

    It doesnt make sense that the device powers up without 32K. Please probe the 32KOUT pin and check the output. You can try using external 32K from a function generator to eliminate crystal issues.

  • 0 in reply to Gandhar Dighe
    Intellectual 300 points

    thanks Gandhar. There were some assembly issue with the PMIC. After doing localized reflow, its working fine.

    Regards,

    Rahul.