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Selecting output capacitor value in TPS40210

manjunath ch
Prodigy 60 points
Other Parts Discussed in Thread: TPS40210

Hi,

I have designed a TPS40210 voltage booster using Ti Web Bench with a specifications :

Vin=10-34v

Vout=48v

Iout=0.5A

And the design I got from Web Bench has a output capacitor of 150uF and it  is working good.  But I need a 8200uF capacitor instead of 150uF for my application. How can i get  48v boosted voltage with a output capacitor value of 8200uF..

Thanks.

  • 0
    TI__Mastermind 39210 points

    Hi Manjunath,

    If you click on the Output Capacitor in the schematic, you will see an Edit Button. Click on that and you can choose from alternate capacitors. If you do not see the cap value you want, click on "Create Custom Cap" at the bottom of the page and add your custom cap value. Let me know if you have any issues with this.

    Alternately you can also edit components from the BOM page using the same method described above.

    Thanks,

  • 0 in reply to Nikhil Gupta (Product Folder Models)
    Prodigy 60 points

    Hi Nikhil,

      I changed the output capacitor value by following your guidance .

    But when i change the Capacitor value from 150uF to 8200uF all other variables in the Booster circuit remains the same.  Changing output capacitor value doesn't effect other variables values  in the circuit..?

    And I did the circuitry practically for the capacitor value of 8200uF But I did not get the expected 48v boosted voltage instead I got 20v output voltage which is same as my input voltage.

    when i replace 8200uF with 150uF output capacitor in same circuit then i can get 48v output voltage from booster circuit.

    so I how can i fix this.

    Thanks.

  • 0 in reply to manjunath ch
    TI__Mastermind 39210 points

    Hi Manjunath,

    When you say that you are getting 20V at the output, did you try this on the actual hardware board?

    Thanks,

  • 0
    Prodigy 60 points
    yes , we did it in the actual hardware board and we noticed that while running the above circuitry with 150uf capacitor it has around 8volts on the soft start pin (SS pin) But while testing with 8200uf capacitor , the SS pin voltage fluctuates between 0V to 1V.

    My Actual application is to use 8200uf capacitor in the output of the 48V.   
    Could you please help on this.  

    Thanks & Regards,
    Manjunath C H

  • 0 in reply to manjunath ch
    TI__Mastermind 39210 points
    With a larger Output Cap, you will need more time to charge it as well. Have you considered increasing the SS cap also?
  • 0 in reply to Nikhil Gupta (Product Folder Models)
    TI__Mastermind 24890 points

    Manjunath,

    Once you update the Cout value manually to 8200uF from 150uF, the other components will not be redesigned for the new Cout. You will have to update the design components accordingly to account for the bigger Cout now.

    As Nikhil has pointed out, the SS cap might need to be increased to a larger value (~33uF) to support the 150uH inductor and 8200uF Cout. This SS cap could cause the converter to take a long time to restart if a fault ever occurs. You could try using a converter with cycle by cycle current limit instead of hiccup. In addition, you might need to make sure the design is stable and/or improve the transient performance by updating the components Rcomp, Ccomp and Ccomp2. You could use the "Re-Comp" tab at the top of the design view to update your compensation design by specifying the range of crossover frequency and phase margin.

    Regards,
    Amod
    WEBENCH Design Center