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BOOSTXL-BATPAKMKII: Voltage Regulators input connections

Pedro Mietto83
Prodigy 130 points
Part Number: BOOSTXL-BATPAKMKII
Other Parts Discussed in Thread: BQ24250, TPS63001, TPS63002

Hi all,

I'd like to understand why, on the BATPAKMKII, the voltage input for the two regulators (U3 3V3, U4 5V) is directly connected to the battery pack, i.e. BAT pins on the BQ24250 charger.

I'd expect the voltage input of those regulators to be connected to the SYS pins of the charger, enabling the system to be supplied by the USB VBUS whenever VBUS available, effectively having the battery pack as a backup power supply.

What's the reasoning for this? Is my understanding of the SYS pins of the battery charger correct?

Thanks in advance.

  • 0
    TI__Genius 10860 points

    Hi Pedro,

    in case you didn't do so yet I'd encourage you to have a look at the Fuel Tank KMII Battery BoosterPack Plug-In Module User's Guide as it describes the Hardware of the BoosterPack you're working with. The User's Guide both describes the signals and the functionality of the different power devices on the  PCB.

    Please come back to us in case there are still pending questions after looking at the document.

    Best regards,

    Britta

  • 0 in reply to Britta Ruelander
    TI__Genius 10860 points
    Hi Pedro,

    did you have the chance to look at the material I've pointed you to?
    As you didn't reply back on my last post I assume that your question has been answered. Please verify the given answer in case it solved your issue.
    Please note that I'll go ahead and close this thread soon if I don't hear back from you.
    Best regards,
    Britta
  • 0 in reply to Britta Ruelander
    Prodigy 130 points

    Hi Britta,

    Thank you for the reply.

    I found this on the User Guide:

    "The input to the TPS63001 is the PAK+_OUT signal directly from the battery. Because of the direct battery connection, configuration of the fuel gauge and Li-Ion charger are irrelevant to this voltage output."

    So I understand the decision to connect voltage input of the regulator to the battery, instead of connecting it to the SYS out from the charger, is just so if you mess up with the charger in any way, the voltage output will not be affected.

    However, the more typical application would be to connect TPS63001 voltage input to the SYS output of the battery charger, correct?

    Best regards.

  • 0 in reply to Pedro Mietto83
    TI__Guru 58215 points
    Hello Pedro,

    The switch inside bq24510 connecting the battery and the system can be turned off via a charger configuration. This means that the power supply of the TPS63001 and TPS63002 is always available as long as a battery is connected to the system, independent of the charger settings or the gas gauge settings.

    I could imagine that there is some load connected to these 2 voltages that shall be available, even if the gas gauge or charger create a fault and disconnect the system from the load. At least I read the explanation in the user's guide this way.

    Best regards,
    Brigitte
  • 0 in reply to Brigitte
    Prodigy 5 points

    I will add this from page 7 of this document.
    Fuel Tank MKII Battery BoosterPack™ Plug-in Module (BOOSTXL‑BATPAKMKII)
    www.ti.com/.../slau618a.pdf


    The bq24250 Li-Ion battery charger provides its own regulated DC-DC output on the SYS pin. In many
    applications this output is used to provide system power. On the Fuel Tank MKII BoosterPack plug-in
    module, this output is placed onto a test point for access (TP4), but not explicitly used to power the
    connected LaunchPad development kit.

    This demonstrates the flexibility of the design.

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