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TPS51315 SIMULATION

eli
Guru 13485 points

Other Parts Discussed in Thread: TPS51315, TPS54620, LM20136, TPS54618, LM20146

 

For Vin=5V,Vout=1.05V/6A,looked at the TPS51315.

I used the SwitcherPro to generate a schematics, only thing I have changed was the output capacitor to a capacitor we do have in hand (T495D227K010R0100) which is  a 220uF/ 10V/ 100mOhm.

I have noticed the report (Analysis - Output1 page) states 377mV as Output ripple p-p.

 Is this is the expected output ripple? This is much above the allowed 50mV ripple for the CPU core ...

I have opened the TINA. The built in example in the TINA is also for 1.05V output with a load of 10Amp so I have used it and run it as is.

The ripple over Vout was few hundreds mV.

I have changed this circuit to match exactly the values presented by the SwitcherPro. The results were much worse than before (reducing the Cout ESR value from 100mOhm down to 10mOhm improved this situation but not better than the original result from TI own example.

 

It is hard for me to exit files, so I can not send you for now the TINA and the SwitcherPro files, but I will appreciate a lot if you can send me a design in SwitcherPro format, or better in the TINA format, that meets my requirements : best if 5V input and   output of : 1.05V / 6Amp / 85c ambient / less than 50mV output

  • 0
    TI__Intellectual 1280 points

    Eli,

    If the 50mV or less output ripple voltage is important to you, you may want to look at another converter.  TPS51315 uses output ripple voltage to directyly control switching so it requires a bit higher ripple voltage than some more standard parts that use opamp feedback to control switching.  I'd recommend the TPS54620 for this application.  I did a design in webench with 4.5V to 5.5V in, 1.05V out @ 6A and chose the TPS54620 in this list of parts.  I took a quick look at the output votlage ripple in the standard design that came out and it was less than 10mV of output voltage ripple with qty 2 22uF ceramic output caps.

    If that solution doesn't work for you there are some other parts like TPS54618, LM20146 and LM20136 that may work for you as well.  You can access webench directly from the main page at www.TI.com

  • 0
    TI__Mastermind 41310 points

    Eli,

    The reference design in TINA has a 10mOhm output capacitor ESR and gives approx. 50mV or ripple on the output. Increasing it to 100mOhm would increase the ripple to >450mV of ripple, tripping the over voltage protection circuit and shutting down the part. I do not believe that the 100mOhm capacitor you have chosen can be used with the part if you are seeking a 1.05V out with less than 50mV ripple.

    If you use equation 13 in the datasheet, the ESR required for the output cap is approximately 10mOhm (for Vout=1.05 and Iout=6A).

    Britt