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TPS63070: Getting More Current at Low Vin

groger57
Intellectual 260 points
Part Number: TPS63070

Hello:

I am using 2x Li 3.6V cell in parallel. With a low dropout cutoff of around 2.0V, I need to get 8V from a boost regulator. The "idle" current is < 100mA, but a "peak" current of about 800mA is required for about 300ms during a transmit sequence. Webench says the best I can get is about 400mA. From what information I can gather, I believe I need a supercap to provide the missing short duration energy. I have not done those calculations yet, but I'm sure there are various sizes and combinations of caps to fill that energy gap.

Does it make sense to use it on the input side, or output side? If either could be used, why is one better than the other? Can someone provide a link to a design that might use such an arrangement? Why does webench not have the option to use a supercap? (asking a bit much maybe?)

Thanks!

  • 0
    TI__Mastermind 21565 points

    Hi Groger:

    Thanks for asking. There won't be too much questions, just take it easy, and we're glad to support you  :-)

    May I know what's the battery you use? As it's not popular for Li battery drop below 2V. 

    For the solution, yes, you could add the super capacitance at the output side, and please make sure the output voltage doesn't exceed the maximum voltage of the supper capacitance.

    WEBENCH is designed more for our device with basic function, but you could download a TINA model and add a huge Cout to do the simulation.

  • 0 in reply to Minqiu Xie
    Intellectual 260 points

    Hi,

    The battery is a Tadiran TL-2300/S. The datasheet does not indicate what the minimum discharge voltage is. I guess 2 volts is a bad assumption? What would it be in general, for 3.6V lithium cells?

    The battery's maximum pulse current is 500mA, this is the reason I wanted to add the supercap.To be safe, how much capacity should I add to reserve for a peak current of 800mA for 350ms? What is the right way to calculate the supercap discharge capacity when used this way?

    Thank you!