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TPS61235 - specifying a lipoly battery?

Barry Klein1
Intellectual 580 points
Other Parts Discussed in Thread: PMP11536

Just received an email containing a link to your Type C power bank reference design.  I see it uses this boost converter.  No-where in the design doc or part spec do I see information related to input current from the battery over the possible range of the battery voltage while full load is applied.

With other competitive parts I see battery currents become excessive to the point the embedded overcurrent protection of the battery can kick in.  In addition the part gets damn hot.  This part has lower on resistance fets though so perhaps thermal is not so much a problem - what do you think - is a heatsink recommended?  Please provide detailed  battery specifications for the reference design and some more data graphs.  Typical battery specs are really lacking in information so we need to know what to ask for for this circuit to work reliably and safely. While doing this you might consider what typical demands are for a power bank product - what products will be charged at 3A by such a power bank and how long must the battery be able to provide the charge?

  • 0
    TI__Mastermind 31580 points
    Hi Barry,

    The TPS61235 is a non isolated dc/dc device, I will move your post to that forum.

    Regards

    Peter
  • 0
    TI__Mastermind 46905 points
    Could you show clearly your question? sorry, but i don't understand the question you want to ask.
  • 0 in reply to Jasper Li
    Intellectual 580 points

    Hi Jasper,

    I have since found this in the design validation report for PMP11536 (below).  Says for battery dropping to 3.2V the current will be 5.26A to maintain 3A 5V Type C charge output.  My point with the original "question" is that a customer would expect to maintain this state for perhaps an hour and a half for a full charge of a tablet or whatever. So what battery is used in the reference design that will maintain this sort of output for this period of time and how hot do things get?  This is not just a worst case example - it is pretty typical.

    In addition to this, the TPS61235 spec discusses a lot about the output but very little about the input current draw.  It is a very important aspect of a design using this part and it is largely ignored.

    I think customers will find that their intended battery will shut down due to overcurrent and in addition will not provide a charge long enough.  But say the customer finds a 10A (!) battery or something - how hot then do things get?  

  • 0 in reply to Barry Klein1
    TI__Mastermind 46905 points
    normally, the battery voltage should be higher than 3.2V, should be at 3.6V level. if the output power is 15W and lasting 1.5h, customer should need 7000mA battery.
    the input current determined by the output current (customer's application condition) and the Efficiency. so we build a device with maximum efficiency and output current capability higher than the requirement. the actual input/output current should be considering by customer.