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WEBENCH® Tools/TPS54160: WEBENCH® Tools/TPS54160: power loss calculation result not accurate in the datasheet

Miller Cai
Prodigy 140 points
Part Number: TPS54160

Tool/software: WEBENCH® Design Tools

Hi,

I need to calculate TPS54160(a integrated MOSFET IC) power loss.

In datasheet, the IC's power loss calculation formula is given, and I use the webench to simulate the IC power loss.

I find the result have a gap between them, the webench's power loss is much bigger than the datasheet formula.

So I test EVM, the webench is right.

When I change the formula(55) 's parameter 0.25 to 0.9, the result is same.

Is the datasheet's formula or parameter have mistake? Or the TPS54160 working in a higher switch time in a period?

  • 0
    TI__Intellectual 1710 points
    Hi Miller,

    Could you please share the input conditions(Vin Min, Vin Max, Vout, Iout and Ta) that you're testing so that we could take a deeper look into this?

    Regards,
    Vishwnath
  • 0 in reply to Vishwanath Tigadi
    TI__Prodigy 140 points

    OK，here is the calculation tools' result:

    TPS54160

    Rds

    Qg

    asw

    tsw

    Vdr(变参)

    Vin(变参)

    Rsns

    Iu

    Vf@0.1(变参)

    Vf@1.5(变参)

    ipp

    fs

    0.18

    3.00E-09

    2.50E-10

    6.00E-09

    24

    24

    1.80E-01

    1.16E-04

    5.50E-01

    5.50E-01

    3.16E-01

    5.00E+05

    L2

    ESRl

    K1

    K2

    x

    y

    Cin

    CinESR

    Cout

    CoutESR

    app

    Iout

    1.80E-05

    8.00E-02

    2.61E-01

    9.20E-01

    1.21E+00

    2.01E+00

    4.70E-06

    5.00E-03

    2.20E-04

    2.50E-02

    1.00E+00

    1.50E+00

    tool’s calculation result

    Pic

    Pmos-conduct

    Pmos-switch

    Pmos-gate

    Pdiode

    Pl,winding

    Pl,core

    Pcin

    Pcout

    The calculation formula and parameter comes from the datasheet and LabKit book

    2.78E-03

    5.59E-02

    1.08E-01

    3.60E-02

    7.12E-01

    1.81E-01

    4.02E-02

    1.33E-03

    2.08E-04

    2E-01

    7.12E-01

    1.9E-1

    1.33E-03

    2.08E-04

    and here is the compare of webench and tools:

    Tool

    Webench

    Pic

    2.78E-03

    2.00E-01

    Pic+P mosfet

    4.80E-01

    Pmos-conduction

    5.59E-02

    Pmos-switch

    1.08E-01

    Pmos-gate

    3.60E-02

    Pdiode

    7.12E-01

    7.12E-01

    Pdiode

    6.95E-01

    Pinductor winding

    1.81E-01

    1.90E-01

    P inductor

    1.61E-01

    Pinductor core

    4.02E-02

    Pcin

    1.33E-03

    1.33E-03

    Pcin

    9.00E-04

    Pcout

    2.08E-04

    2.08E-04

    Pcout

    2.98E-04

    So you can see the gap between the webench result and my tools result.

    The IC power loss is not accurate and I think the parameter of the IC MOSFET is not right.

    What's your view about the gap?

  • 0 in reply to Miller Cai
    TI__Guru**** 191445 points
    It is somewhat difficult to accurately calculate power loss. Webench uses actual measured data to model the power losses, so I would expect the Webench results to be more accurate in most cases.
  • 0 in reply to JohnTucker
    TI__Prodigy 140 points
    I focus on the TPS54160's datasheet parameter, it provides a formula and calculation parameter,but not match with the webench and real, I want to figure out the reason.
  • 0 in reply to Miller Cai
    TI__Guru**** 191445 points
    One thing to note. The terms in equation 58 should be added, not multiplied. Does that help?
  • 0 in reply to JohnTucker
    TI__Prodigy 140 points
    I do that... and I tell BU's marketing the typo.
    Maybe you can calculate the power loss of the IC and finding there is a big gap between the formula and webench
  • 0 in reply to Miller Cai
    TI__Intellectual 1710 points
    Hi Miller,

    Webench calculates switching losses considering rise and fall time of mosfet turn on and turn off. Webench also takes temperature effects on RDS into account. These are not accounted for in datasheet. Also we tweak few parameters from datasheet value to make Efficiency more accurate.

    I've tabulated the losses below:

    Power dissipation Miller's tool Webench Difference
    IC IQ PD 2.78E-03 3.31E-04 0.0024488
    Pswitching 1.08E-01 0.2841 0.1761
    Pconduction 5.59E-02 0.0967 0.0408
    Pgate 3.60E-02 0.08036 0.04436

    Regards,
    Vishwanath
  • 0 in reply to Vishwanath Tigadi
    TI__Intellectual 1710 points
    Power dissipation_____Miller's tool_____Webench_________Difference
    IC IQ PD_____________2.78E-03________3.31E-04__________0.0024488
    Pswitching___________1.08E-01________0.2841___________0.1761
    Pconduction_________5.59E-02________0.0967___________0.0408
    Pgate_______________3.60E-02________0.08036__________0.04436

    Sorry about the spacing
  • 0 in reply to Vishwanath Tigadi
    TI__Prodigy 140 points
    I can see the biggest gap between webench and my tools is P mosfet switching.
    So in the webench calculation, you double the Pswithcing for it consisting of turn on+turn off? Or you just tweak the parameter?
  • 0 in reply to Miller Cai
    TI__Intellectual 1710 points
    To be more precise, The datasheet equation is calculating only the Coss Losses considering Coss to be 250 pF. Webench however also accounts for the additional conduction loss during switching(taking tr and tf). sum of these 2 losses will give you total switching loss. Datasheet doesn't display equation for the second part.