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TPS54318 / webench efficiency simulation

Tsukui Yusuke
Guru 21930 points

Hi,

Could you tell me about efficiency simulation.
Customer simulated following conditions.
◇Vin=3.3V to 5V,Vout=1.1V,Iout=3A

I got the following questions about the simulation.
1．The reason more 5V is more efficient than 3.3V


8688.WebenchReportsServlet.pdf

2.Does Webench perform simulation of the voltage of Boot strap at 5V?
　 Or Change the voltage according to the input voltage?

Could you give me your advice?

Best Regards,
Yusuke/Japan Disty

  • 0
    TI__Intellectual 890 points
    Hi Yusuke-san,

    Efficiency is a function of many parameters like FET gate charge(Qg), rise(Tr)/fall time(Tf), rdson etc. For your design, at 3A the conduction losses (i.e Irms^2*Rdson) are more dominant. Rdson which contributes to the conduction loss is higher at 3.3V Vin than the rdson at 5V and as a result you see higher efficiency at 5V in that region. Now at light loads (~0.6A) switching losses are more dominant. Qg and Tr/Tf which is a function of Vin and contributes to switching losses are lower at 3.3V, hence the efficiency in that region is higher for 3.3V Vin.

    The boot strap voltage is set to 5V.

    Regards,
    -Abhishek