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AM3352: PMIC_POWER_EN is not asserted

Kuerbis
Expert 4145 points
Part Number: AM3352

Hi Team,

 

The customer observed PMIC_POWER_EN is not asserted to high during POR on their several production boards.

We confirmed EXT_WAKEUP is around 1.78V.

The device is as below.

AM3352BZCZ60

TPS65910AA1RSL

 

Q1. Do you have any idea for this issue?

 

The AM335x and TPS65910x schematic checklists are compliant except for the following items of AM335x. Their connection is that RTC_XTALOUT is NC, but RTC_XTALIN is pulled down.

Q1. Is there a possibility the issue which PMIC_POWER_EN is not asserted by RTC_XTALIN is pulled down?

 

2.5 Clocking

If you do not need RTC-only mode and the RTC timer feature, you do not need to include a 32 KHz

crystal. The 32 KHz reference can come from the high frequency clock. Leave the RTC_XTALIN/RTC_XTALOUT pins as NC.

 

AM335x Schematic Checklist

http://www.ti.com/lit/an/sprabn2a/sprabn2a.pdf

TPS65910x Schematic Checklist

https://www.ti.com/lit/an/swca139b/swca139b.pdf

 

Thanks and Best regards,

Kuerbis

  • 0 in reply to Biser Gatchev-XID
    TI__Expert 4145 points

    Hi Biser,

     

    Thank you for the E2E link. It’s very helpful.

    I would like to see http://www.ti.com/lit/an/sprabn2/sprabn2.pdf. But the link is broken.

    There is table2 in the latest version.

    Would you please provide it?

     

    In customer’s system, RTC is not used, the following two options are the recommended solutions. Correct?

    a) connect RTC_PORz to PORz. This was recommended in below E2E thread.

    e2e.ti.com/.../755784

    b) connect RTC_PORz to VSS(GND). This is recommended in table 2 below document.

    www.ti.com/.../sprabn2.pdf

     

    Thanks and Best regards,

     Kuerbis

  • 0 in reply to Kuerbis
    TI__Genius 13567 points

    Hi Kuerbis,

    The PMIC_POWER_EN pin is driven by the RTC subsystem. If the RTC_PORz is tied to VSS (GND) then the RTC subsystem is inactive and this pin will be not driven high.

  • 0 in reply to Ahmad_Rashed
    TI__Expert 4145 points

    Hi Ahmad,

     

    Please let me confirm.

    Is your reply which The PMIC_POWER_EN pin will be not driven high for the following RTC Feature Disabled mode?

    If your application never uses the RTC functionality, connect RTC_KALDO_ENn to VDDS_RTC,

    CAP_VDD_RTC to VDD_CORE, and RTC_PWRONRSTn to ground. These connections disable the

    internal RTC LDO because RTC_KALDO_ENn is high, and they use the external VDD_CORE supply to

    power the RTC digital core. The RTC LDO must be disabled for internal power sequencing even though

    the RTC is not used. Grounding the reset signal will ensure the RTC stays in reset. Disabling the internal

    LDO will allow the application to achieve lower power consumption in all the low power modes.

     

    If your application uses the RTC functionality and requires RTC-only mode with following connections, the PMIC_POWER_EN pin will be driven high. Correct?

    • RTC_KALDO_ENn is grounded

    • CAP_VDD_RTC is connected to 1uF decoupling capacitor to ground

    • RTC_PWRONRSTn is connected to 1.8V RTC power on reset

    • PMIC_POWER_EN is connected to power input of PMIC

    • EXT_WAKEUP0 is connected to a wakeup source

     

    Thanks and Best regards,

    Kuerbis

  • 0 in reply to Kuerbis
    TI__Genius 13567 points

    That table was never meant for designs using a PMIC due to the hand-shake between PMIC and RTC Subystem (PMIC_POWER_EN). We always recommend following the Sitara + PMIC user guides provided on the PMIC product page.

    If you followed the "RTC feature disabled" mode then you can un-disable the RTCSS by connecting RTC_PORz to normal PORz. This will not support RTC-only mode but it will leave the RTCSS alive. If you keep the RTCSS in reset we've had customers find software crashes after any register reads to the RTC register space.

  • 0 in reply to Ahmad_Rashed
    TI__Expert 4145 points

    Hi Ahmad,

     

    I'm sorry. I accidentally pressed the Resolve button. I have the following questions.

     

    > That table was never meant for designs using a PMIC due to the hand-shake between PMIC and RTC Subystem (PMIC_POWER_EN). We always recommend following the Sitara + PMIC user guides provided on the PMIC product page.

     

    There is no description the table for the connection of each RTC mode in TPS65910Ax User's Guide for AM335x Processors. AM335x Schematic Checklist used have it. But it was removed in the latest version.

    Q1. Where can I get that information?

    TPS65910Ax User's Guide for AM335x Processors

    http://www.tij.co.jp/jp/lit/ug/swcu093f/swcu093f.pdf

     

    Q2, Do you mean that the recommendation is to un-disable the RTCSS by connecting RTC_PORz to normal PORz for the "RTC feature disabled"?

     

    Thanks and Best regards,

    Kuerbis