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TPS65910A / Power Down Sequence for AM3352

Ryuji
Guru 20090 points
Other Parts Discussed in Thread: AM3352, TPS65910A, TPS65910, AM3354
Hello,
 
I can found the AM3352 request sequence power down as below from datasheet P103 4.1.2.
"The preferred way to sequence power down is to have all the power supplies ramped down sequentially in
the exact reverse order of the power-up sequencing."
However , I couldn't find the power down sequnce which can correspond AM3352 power down sequence from the TPS65910A datasheet and user's guide for AM335x.
 
<Q1>
Can TPS65910A become adapted to the power-down sequence of AM3352?
If yes, please let me know the setting method.
 
<Q2>
Can we control TPS65910A Power on/off by PWRON pin by Power Up/Down sequence for AM3352?
 
Best Regards,
Ryuji Asaka
  • 0
    TI__Expert 6090 points

    1. there is no power down sequnce for TPS65910. All rails power off simultaneously. it is just the cap and load on which the timing of rails going down depends.

    2.  Yes PWRON pin can be used to control the power on and off of PMIC.

  • 0 in reply to Puneet Sehgal
    Guru 20090 points
    Hello Puneet san,
     
    Thank you.
    I understood.
     
    Best Regards,
    Ryuji Asaka
  • 0 in reply to Puneet Sehgal
    Prodigy 140 points

    Hi Puneet,

    In our application, we are using the PMIC TPS65910A3A1RSL to power AM3354. All rails are working and the AM3354 is also working well.

    In our application we have a need to reboot the AM3354 (say after a firmware upgrade). We do this by pulling the PWON pin on the PMIC (long press off). I noticed that al the rails on the PMIC go down to zero except VMMC and VAUX2.

    Normally, the VMCC rail is at 3.3V in our application and goes down to 2.5V and stays there when PWON is pulled lo.

    VAUX2 which is normally at 3.3V goes down to 1.8V and stays there when PWON is pulled lo.

    Both rails come back to 3.3V after PWON is released. The AM3354 which normally boots from the SD card fails to boot and the spew "ccccccccccc...." appears on the serial port. If I eject the SD card and re-insert, the AM3354 boots successfully !

    My questions are :

    1. Why don't the power rails VMMC and VUX2 go down to zero (like other rails) when PWON is pulled lo ?

    2. Do you think the voltage on the rails violate the power down / up sequnce and cause the AM3354 not to boot ?

    Thx for your answers in advance

    Vishy

  • 0 in reply to Vishy Canadam
    TI__Expert 6090 points

    Vishy,

    1, what is connected to VMMC and VUAX2 ? What is the input suplly to board? can you please share the schematic.

    2. PMIC does not have any power off sequnce , all rails goes off simultaneously. Rails goes off at same time it is just the load and capacitance on the line which times the decay of rails.