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AM3352: RTC and discrete power solution

Mukul Bhatnagar
Guru* 83855 points
Part Number: AM3352

Posting on behalf of the field team 

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One of my customers designing IOT gateway based on  AM335x (300 MHz) device without PMIC to save the cost. But they need the RTC feature. From the power perspective only the power sequencing needs to be done and as DVFS is not supported and we support only the DS1 , no Linux driver is required here right ?

 Also they need some mechanism to wake up the system from internally like the RTC alarm. For this they can use the AM335x internal RTC right ?

  • 0
    TI__Guru**** 393215 points
    Hi Mukul.

    Per AM335x TRM Deepsleep1 presumes that:

    VDD_MPU = 0.95 V (nom)
    VDD_CORE = 0.95 V (nom)

    As for wakeup, yes, RTC alarm is supported.
  • 0
    TI__Genius 16690 points

    VDD_CORE and VDD_MPU power supplies always need to be powered up at 1.1V during boot (advisory 1.0.24). The voltage can either stay at 1.1V for 300MHz MPU or can be reduced at 0.95V. If DVFS is not used, the core voltage has to be always at 1.1V. 

    Advisory 1.0.24 Boot: System Boot is Not Reliable if Reset is Asserted While Operating in OPP50

    Regarding DS1, I don't think DS1 is currently not supported in Linux. Why do you need to use DS1 instead of DS0 ? 

  • 0 in reply to kshin
    TI__Expert 8550 points

    Shin,

    thanks for pointing to the erratum, so will make sure we take care of power up requirements as per 1.0.24. As far as DVFS (to scale down to 0.95) is concerned can that be achieved without the PMIC ? Do we have any reference schematics/guidelines etc ?

  • 0 in reply to Shivasharan Nagalikar
    TI__Genius 16690 points

    Shiv,

    If the goal is a low cost discrete power solution, it would be better not supporting DVFS if power in low power mode is not a concern. You can design your power solution with fixed 1.1V core power rails (VDD_CORE and VDD_MPU).  You can still use suspend or standy from Linux w/o scaling core voltage from 1.1V to 0.95V. Linux PMIC driver might need to be looked at for this change (no voltage scaling in low power mode).