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TPS65951 wont start AM3703 (INT1 permanent low), first boot

Thomas Leidenfrost
Prodigy 250 points
Other Parts Discussed in Thread: AM3703

We got this issue with approx. 15% of our new manufactured boards, which are unprogrammed. What we already know:

Supply voltages present: VDD1 & VDD2 = 1V2, VIO = 1V8, VRTC.OUT = 1V5. VBAT is ~ 3V8

26 MHz Clock present at PMU 2-3 ms after oscillator is powered, looped from PMU (32CLKOUT)  to AM3703 sys_Xtalin (also present there)

32.768 kHz RTC-Clock present at PMU, looped from PMU (HFCLKOUT) to AM3703 sys_32k (also present there)

CLKREQ from AM3703 to PMU is HIGH (not active)

PMU NRESWARM & NRESPWRON are HIGH (not in reset)

That means power sequencing as in datasheet chapter 6.5.4.2 is complete & fine

But VDAC.OUT & VPPL2.OUT keep low as INT1 from PMU to AM3703 (SYS_NIRQ) does

We have no external RTC, no USB present, no charger present,

Boot Mode is set to Master (Boot1 with 10k pull-down o GND, Boot0 with 10k pull-up to VBAT (3V8))

Any hint is welcome. What causes INT1 keeping permanent low?

Thomas

  • 0
    TI__Intellectual 2045 points

    Thomas,

     

    VDAC and VPLL2 are not part of the power up sequence. this LDOs must be enabled by sofware. if you don't have any software flashed then it's normal to have them staying low.

    INT line is the interrupt line which is active low, at boot you will always have an interrupt trigged as all switch-on event trig an interrupt(PWRON, main battery plugged, vbus plug,..). If there is no software flashed then nobody will clear the interrupt and the line will stay low.

     

    By the way, i do not understand below senstence:

    26 MHz Clock present at PMU 2-3 ms after oscillator is powered, looped from PMU (32CLKOUT)  to AM3703 sys_Xtalin (also present there)

    32.768 kHz RTC-Clock present at PMU, looped from PMU (HFCLKOUT) to AM3703 sys_32k (also present there)

     

    PMIC 32CLKOUT should be connected to AM sys_32k and PMIC HFCLKOUT shout be connected to AM sys_Xtalin.

    a 32KHz crystal should be connected to pmic

    a 26MHz oscillator shoudl be connected to PMIC HFCLKIN and controlled by PMIC CLKEN

    Is tit the case?

    could you share the schematic?

    regards,Alexis

  • 0 in reply to Alexis Piton
    Prodigy 250 points

    Thanks for reply Alexis.

    You are right, my description was wrong, but the schematic is as you said. Pls have a look here.

    The confusing part is that the INT1 phenomen occurs after several successful starts from µSD-Card (MMC1) or even on new boards.

    For delevopment we have the firmware on SD-Card, which is not first in boot sequence, but with an empty NAND, no USB & UART3 for debugging only it should boot from MMC1 latest. Changing the card does not help. Our flash & Ram is MT46H64M32LFCM-6 IT & MT29F4G16ABBDAHC-IT

  • 0 in reply to Thomas Leidenfrost
    TI__Intellectual 2045 points

    Thomas,

     

    Could you clarify what is the issue.

    having PMIC INT1 line low at boot is normal, please clearly describe what is the issue and what happens on INT1 line on a working case and a failling case.

     

    regards,

    Alexis

  • 0 in reply to Alexis Piton
    Prodigy 250 points

    Hi Alexis,

    on a working unit INT1 does not keep permanent low after start up.

    I would like to know why INT1 at some of our boards is permanent low, after power up. The system does not boot

    The only output at Uart3 is

    U-Boot SPL 2012.07 (Oct 25 2012 - 10:13:30)
    Texas Instruments Revision detection unimplemented

    Than nothing happens, INT1 keeps low

  • 0 in reply to Thomas Leidenfrost
    TI__Intellectual 2045 points

    Thomas,

    INT1 line will stay low until software clear the interrupt source, if the processor does not boot, INT1 line will stay low.

    is the PMIC NRESPWRON signal rises?(on pmic side and processor side).

    Regarding UART trace, you should post a request on AM forum

     

    alexis

  • 0 in reply to Alexis Piton
    Prodigy 250 points

    Thanks

    Yes, NRESPWRON rises.