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AM335X Powered by TPS65910AA1

Peng Liu50174
Expert 1500 points
Other Parts Discussed in Thread: AM3357

Hi,

I'm using TPS65910AA1 to power AM3357. The PMIC's PWRHOLD is connected from processor's PMIC_POWER_EN signal, and the PMIC's PWRON is connected to a button witch. We found that once the power is supplied to the board, without pressing the button to trig one PWRON Low event, the PMIC automatically powers up the processor. I just like to know if PWRON can be used to control TPS65910AA1  power. I saw there is a graph in the fig.5 of the datasheet, but I don't know if it applicable to TPS65910AA1 too.

Thanks,

 

 

  • 0
    TI__Guru**** 393215 points
    Hi Liu,
     
    If you disconnect PWRHOLD from PMIC_POWER_EN and connect it to PMIC VAUX33 or VIO (through a 10kOhm resistor) the PWRON button should function as you wish.
  • 0 in reply to Biser Gatchev-XID
    Expert 1500 points

    Hi, Biser,

    I just wonder how to use PMIC_POWER_EN from AM3357.  Does AM335X always assert PMIC_POWER_EN  When the VDDS_RTC is available?

    From the AM335X Technical Reference Manual, Rev.G. Figure 8-5. High Level System View for RTC-only Mode, it shows PMIC_POWER_EN  is asserted by AM335X when EXT_WAKEUP is asserted in the RTC_ONLY mode. When will the RTC_ONLY mode be entered?  When the VDDS_RTC power is first applied while the other power are still OFF, what is the mode of the AM335X?

    Thanks,

    Peng

  • 0 in reply to Peng Liu50174
    TI__Guru**** 393215 points
    Hi Peng,
     
    RTC-only mode is a low power mode (power management is described in AM335X TRM section 8.1.4). When the VDDS_RTC power is first applied while the other power are still OFF the AM335X isn't in any mode, it's still in reset. A bit more is explained for PMIC_POWER_EN in section 2.3.3.8 of the AM335X TRM.
  • 0 in reply to Biser Gatchev-XID
    Expert 1500 points

    Hi, Biser,

    There is no  section 2.3.3.8 in TRM Rev.G. But I found in RTC_PMIC Register, the defaut value of PWR_ENABLE_EN is 0, which means pmic_power_en signal will always be driven as 1, ON state. This explains why PWR_ENABLE_EN  is alway high on our board once VDDS_RTC is supplied before S/W is running.

    Now I have some questions about TPS65910AA1. In its datasheet, there is Figure 4. Device Turn-On/Off with Rising/Falling Input Voltage. Does this correpond to Device automatically switches on at NO SUPPLY-to-OFF or BACKUP-to-OFF transition (i.e VMBHI_IT_MSK=0)? And Figure 5. PWRON Turn-On/Turn-Off relates to VMBHI_IT_MSK=1?

    Thanks,

     

  • 0 in reply to Peng Liu50174
    TI__Guru**** 393215 points
    Sorry, my typo. It's section 20.3.3.8.
     
    Yes, you are correct about Figure 4. Figure 5 is the PWRON switch on/off sequence. I'm not sure how this relates to VMBHI_IT_MSK=1. There is a TPS659XX power supply forum, where they should be able to answer this better: http://e2e.ti.com/support/power_management/pmu/f/43.aspx.