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WEBENCH® Tools/TPS53315: Variation the Rtrip value.

Karthik B
Expert 1310 points

Part Number: TPS53315

Tool/software: WEBENCH® Design Tools

Hi,

In Webench the value for the Rtrip=40.2k,is used for the design in which;

  • Vin=5v
  • Iout=4A
  • Vout=3.3v

But using the formula that is mentioned in the TPS53315 datasheet( pg.no 19, Equation 10) we get Rtrip=25.032k ,when considering the above mentioned design values.

Similarly, The Cout cap of 470uF non ceramic cap is used in the webench in the design with;

  • Vin=5V
  • Vout=1V
  • Iout=10A

But, using the equation 2 (pg no.13) of the datasheet & when substituted with Cout=470uF donot satisy the condition that is specified in equation 2  . How Cout is being selected ?Can i use 680uF cap instead of 470uF?

why Webench is showing such high variation , which value should i select for Rtrip and Cout ?

Please help me.

Regards,

Karthik

  • 0
    TI__Guru**** 191445 points
    This should probably be moved to the Webench forum. Can you share your webench design for analysis? You can send it from inside Webench to j(dash)tucker(at)ti(dot)com.
  • 0
    TI__Intellectual 1710 points
    Hi Karthik,

    Webench uses same equation to calculate Rtrip as Datasheet. But Webench limits the value between 40k Ohm to 240k Ohm.

    Cout selection is a little different. It takes Vout ripple factor , Irms current through the capacitor, Voltage derating, power loss and few other parameters into consideration while selecting Cout capacitor. However you can click on select alternate parts in the BOM page. You can see that 470uF is also in the list of alternate solutions for Cout.

    Regards,
    Vishwanath