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TPS563209: design for low current application

Harikant gujarathi
Prodigy 30 points
Part Number: TPS563209
Other Parts Discussed in Thread: TPS561208, TPS560200

I need to use this part for low current output. Input is 12V and output is 3.3V@0.2A for one application and for another application input is 12V and output is 5V@0.15A. It is my understanding to use higher inductor around 10uH instead of 2.2uH as recommended in the data sheet. In data sheet table is provided for selection of inductor, output cap and feedback resistors but not provided what is the input, output current. Especially inductor value can not be generalised as it depends on input  and  output current. In webench also it is suggested for 2.2uH, and 3.3uH for these applications. Is there any specific reason to use these inductor values? Please suggest. Also please suggest for the procedure to reduce over current limit. 

Thanks, Harikant

  • 0
    TI__Expert 4875 points
    Hi Harikant,

    For the datasheet table, it is basically set for 12Vin. So the inductor value is good for your application. For low current use, I will only recommend you to choose the max recommended inductor value in the table. The inductor value will not only change the inductor current ripple but also will affect loop response. The value in the table is considered both factor.

    For overcurrent limit, it is internally fixed by design. You could not adjust it externally. I would like to let you know that we have TPS560200 and TPS561208(1A) which may be more close to your current level. Thanks!
  • 0 in reply to Anthony Lang
    Prodigy 30 points

    Hi Anthony,

    Thanks for your reply. Using 2.2uH, inductor current swing is around 2A and using 4.7uH (max value in the table) swing is around 1A. Is this ok for 200mA output load. Yes by increasing inductor value, loop response is disturbed, can it be possible by reducing output capacitor value, response loop can be maintained. Please suggest.

    Thanks and Regards

    Harikant

  • 0 in reply to Harikant gujarathi
    TI__Expert 4875 points
    Hi Harikant,

    Yes, 4.7uH is good. And there is no need to adjust output cap for loop response. You will still get good phase margin with 4.7uH and the same value output cap. Thanks!
  • 0 in reply to Anthony Lang
    Prodigy 30 points

    Hi 

    Thanks for the reply. Design will be finalize using 4.7uH.

    Thanks and Regards

    Harikant