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TPS62730: incorrect equation in datasheet?

Paul Schoenke
Expert 1375 points
Other Parts Discussed in Thread: TPS62730

Hello:

I am using the TPS62730 with the TI CC110 device for reducing current draw off of battery as recommended.

Datasheet discusses how to calculate the current ripple that’s expected from the switcher with the equation #4 on page 12.  This equation appears to be wrong and our calculations show ~1.9A which couldn’t possibly be correct since this device is optimized to run off of a battery.  We are seeing 100uA of ripple, is this typical or reasonable?  Would there be an inductor recommendation?  Is there an error in the equations for this part?  There seems to be a multiplication factor missing?

We are also getting about 200uA spike at switching frequency also in this application. 

Any feedback or input is welcomed and appreciated!

Thanks again!

Paul

  • 0
    TI__Expert 7110 points
    Can you please give me the numbers you where using for your calculations?

    Please consider basically that this equation returns the ripple current in the inductor, which is different from the current that is drawn by the battery.
    Page 12 shows two inductors we recommend.

    Depending on the amount of input capacitance you use at the DC/DC, you get a certain value of ac current drawn from the battery. This can be higher, if you use the minimum required capacitance and is getting lower (ac wise) with a higher capacitance.