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TPS65217: Is it possible to change the default values of the PPATH register so that the current is limited on the AC input on power-up?

James La Haye
Prodigy 20 points
Part Number: TPS65217

Hi, I'm working with the TPS65217 and I noticed that on power up of the Octavo processor (OSD3358-512M-IND) the in-rush current peaks at ~3.14A on the 5.0V AC input (see tek00016.png). However, when I do the same thing from the USB input I get a peak in-rush current of ~1.09A (see tek00017.png).

After researching the PMIC, I see that the input current can be limited to certain values (see TPS65217_page_44.pdf). My question is: is it possible to change the reset values of this register so that the AC and USB inputs are limited to 100mA on power-up? I need the reset values to be changed so that the part boots up in that state to limit the in-rush current.

Thanks for your help,

James

tps65217_page_44.pdf

  • 0
    TI__Prodigy 450 points
    Hi James,

    Thank you for your question. I have assigned your request to the responsible engineer and we will get back to you as soon as possible.

    Regards,
    Kevin
  • 0
    TI__Mastermind 30310 points

    James,

    The reset values of the TPS65217C register map are programmed at the TI factory before it is assembled in the SIP package at Octavo for the OSD335x family.

    The reset value of the TPS65217 cannot be permanently changed by the end customer. You may want to reach out to Octavo to see what they tested in the lab when they characterized the SIP packaged product on a PCB using the recommended passive values.

    In order to look into this matter any further, you will need to attach a schematic showing that the recommended capacitance values on page 6, Table 2.1. OSD335x Passives, of the OSD335x datasheet have been followed for power pins when Device column reads "TPS65217C" (for example VIN_5V = AC with C = 10uF)

  • 0 in reply to Brian Berner
    Prodigy 20 points

      Hi Brian,  thanks for getting back to me. My understanding of Table 6 is that it lists the *integrated* passives of the OSD335x to those externally accessible pins. In other words, the capacitance listed is already included within the device for those pins. As for external passives, we followed capacitance scheme used in the Octavo reference design. We also looked at the BeagleBone reference design as well.

      In any case, the info you gave me about the TPS65217C register map being programmed at the TI factory answers my question. I'll take up the in-rush current issue with Octavo and see what they recommend.

      Thank you very much for your help!

    James  

    page_6_OSD335x_datasheet.pdf

  • 0 in reply to James La Haye
    TI__Mastermind 30310 points
    James,

    Thanks for the correction! You are right: Octavo integrated over 140 caps, resistors, inductors, and ferrite beads into the OSD335x package.

    Let me know when you hear back from Octavo regarding in-rush current. I am curious about their results and explanation.
  • 0 in reply to Brian Berner
    TI__Mastermind 30310 points
    P.S. there is a note in the Applications Guide that says "However, you may want to add additional bulk capacitors on input and output power rails depending on your application." octavosystems.com/.../