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AM335x PMIC_POWER_EN signal without RTC

ay0689_3
Expert 1085 points
Other Parts Discussed in Thread: TPS65910, AM3352, TMDXEVM3358, TPS65910A

Hello, I connect PWRHOLD signal of TPS65910 to AM3352 PMIC_PWR_EN.

I do not use AM3352 On-chip RTC and 32k Crystal circuits are not assembled.

In this case, is PMIC_PWR_EN signal able to outputted High-level after supplying VDDS_RTC ?

In the other words, is PMIC_PWR_EN behaved correctly without 32k Crystal circuits ?

Best regards

ay0689

  • 0
    TI__Guru**** 393215 points
    Hi,

    For proper connection please check processors.wiki.ti.com/.../AM335x_Schematic_Checklist See also section 20.3.3.8from the AM335x TRM Rev. N. PMIC_POWER_EN is high at reset release time, but you will not be able to shutdown the system properly if you do not implement the RTC timer functionality (without RTC-only mode).
  • 0 in reply to Biser Gatchev-XID
    Expert 1085 points

    Hello Biser-san,　

    I checked the wiki and I verified that my RTC setting is RTC Only Mode without 32.768KHz as follows.

    I made 3 sheets of slides for more detailed information about our AM3352 PMIC_POWER_EN Failure.　　　　　　　　　　　　　　　　　　　　　　　　　　　　

    I think that PLL Based 32.768KHz Clock can not be supplied to RTC_SS because POWER "VDDS_RTC" is only supplied to AM3352.

    Is there any relation between PMIC_POWER_EN signal and 32.768KHz CLOCK ?

    Best regards,

    AY0689

  • 0 in reply to ay0689_3
    TI__Guru**** 393215 points
    This has been escalated to the factory team. Sorry for the delay, they will reply directly here as soon as possible.
  • 0 in reply to Biser Gatchev-XID
    Expert 1085 points

    Hello,I inform you of the result of the additional experiment.

    I added 32.768KHz OSC Module to AM3352 RTC_XTAL_IN signal.

    The following slide 4 is the result.

    best regards,

    ay0689

  • 0 in reply to ay0689_3
    TI__Guru 55265 points

    The PMIC_POWER_EN should go high without an external 32.768KHz crystal connected.

    The schematic portions posted do not show your connection for CAP_VDD_RTC, RTC_KALDO_EN, and RTC_PWRONRSTn.

    Are you using the internal RTC LDO or an external 1.1v source to power the RTC core supply?

    If you are using the internal RTC LDO, you must hold RTC_PWRONRSTn low for at least 1ms after VDDS_RTC becomes valid.

    If using an external 1.1v source, you must hold RTC_PWRONRSTn low until VDDS_RTC and CAP_VDD_RTC becomes valid.

    Please verify you are providing the correct power-up/reset sequence on the intermittent systems.

    Are you checking the state of the actual PMIC_POWER_EN output signal from AM335x or assuming it does not go high because the PMIC doesn’t power-up?  If not, you may need to check the state of this signal to confirm the issue is not related to the PMIC.

    Regards,
    Paul

  • 0 in reply to peaves
    Expert 1085 points

    Hello Paul-san,

    The schematic portions posted do not show your connection for CAP_VDD_RTC, RTC_KALDO_EN, and RTC_PWRONRSTn.

    As I mentioned slide #1 ,

    CAP_VDD_RTC => 1uF Decoupling Cap to VSS

    RTC_KALDO_EN => VSS

    RTC_PWRONRSTn => 4.7K Pull-up by VDDS_RTC

    Are you using the internal RTC LDO => Yes  or an external 1.1v source to power the RTC core supply? => No

    If you are using the internal RTC LDO, you must hold RTC_PWRONRSTn low for at least 1ms after VDDS_RTC becomes valid.

    => use internal RTC LDO but RTC_PWRONRSTn is always H-level (4.7K pulled up Resistor by VDDS_RTC).

    The RTC circuits are based on TMDXEVM3358　Evaluation Module.  

    Schematic: www.tij.co.jp/.../getliterature.tsp

    Are you checking the state of the actual PMIC_POWER_EN output signal from AM335x or assuming it does not go high because the PMIC doesn’t power-up?

    If not, you may need to check the state of this signal to confirm the issue is not related to the PMIC.

    We verified the followings so far.

    -PMIC_POWER_EN from AM3352 does not output H-Level rarely.

    -PMIC_POWER_EN is also connected to PWRHOLD signal of TPS65910.

    Can the PMIC_POWER_EN Signal be opreated on our setting(RTC-only mode w/o 32.768KHz Crystal and RTC_PWRONRSTn is always High) ?  

    Best regards,

    ay0689

  • 0 in reply to ay0689_3
    TI__Guru 55265 points

    The RTC_PWRONRSTn input must be held low at least 1ms after VDDS_RTC becomes valid to provide a proper reset to the RTC circuits.  This delay is implemented with U6A, R69, and C114 on the AM335x GP EVM.

    Regards,
    Paul

  • 0 in reply to peaves
    Expert 1085 points

    Hello, Paul-san,

    In reply to ay0689_2:

    The PMIC_POWER_EN should go high without an external 32.768KHz crystal connected.

    Again, I summarize the connection state of our board.

    　We do not use AM3352 RTC Module.

    　We designed our AM3352 board as the following connections;

    1.  RTC Only Mode w/o 32.768Hz Crystal.
    2.  RTC_POWERONRSTn signal is always supplied by High-level. (Not supplying 1ms Low pulse)

    With above AM3352 connections, does PMIC_POWER_EN signal generate High-level signal to trigger the other PMIC power outputs?  

    Are our board connections correct in terns of AM3352 operation? 

    Best regards,

    ay0689

  • 0 in reply to ay0689_3
    Expert 1085 points

    Hello Paul-san,

    Since it is getting harder to find problems on the AM3352 side, we would like to review the problems on the PMIC side.

    As a condition that the PMIC_POWER_EN signal does not come out, the supply current of VRTC is suspected.
    From the data sheet of the PMIC it turned out that when the PMIC enters the Backup-Mode, the supply current from VRTC is extremely reduced.

    When the PMIC is in this Backup-Mode, is there a possibility that the AM3352 will run out of current and the PMIC_POWER_EN signal can not be output?

    Best regards,

    ay0689

  • 0 in reply to ay0689_3
    TI__Guru**** 393215 points
    Which revision of TPS65910A are you using?
  • 0 in reply to Biser Gatchev-XID
    Expert 1085 points

    Hello, Biser-san,

    The device P.N. is  "TPS65910AA1RSL".

    Please see the following picture regarding the device symbol.

    Could you please tell me how to identify the revision of this PMIC device? 

    In addition, I took a picture of AM3352 device.

     

    Best regards,

    ay0689

  • 0 in reply to ay0689_3
    TI__Guru**** 393215 points
    I suppose you are using DDR2 memory, if you use TPS65910AA1RSL. Otherwise yes, this PMIC revision outputs <100uA in backup mode. You should check what happens with the VDDS_RTC power rail during power state transitions.