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Original question:

UCD74120

UCD74120: UCD74120: Power Loss/Efficiency data

SteeVeeDee
Intellectual 700 points
Part Number: UCD74120

Elsewhere in this forum there is a thread with an efficiency graph of the UCD74120 operating at 500 kHz with an inductor ESR of 1.2 mOhm.

We need similar data for:

Vin = 12V, Vout = 0.9V,  inductor ESR = 3 mOhm,typ (Coilcraft XEL5030, 0.42 uH), F,sw = 1000 kHz, generally 10-15A per phase.

Can you please provide more comprehensive data?

Thanks, Best, Steve

  • 0
    Intellectual 700 points

    TI Team-

    Haven't heard a response on this yet- any help that you can provide would be appreciated.

    Thanks, Best, Steve

  • 0 in reply to SteeVeeDee
    TI__Mastermind 24075 points
    Hi Steve,

    Sorry, we missed your question.
    We will take a look and reply to you.

    Thanks
    Qian
  • 0
    TI__Genius 13700 points

    Steve,

    I have been unable to locate any additional characterization curves for efficiency for the UCD74120 and unfortunately a standalone EVM for this device does not exist.

    It is included in several of our DSP EVMs, in particular the 66AK2H Evaluation Module (K2EVMHK) but these would are not set up to easily perform efficiency tests at under various test conditions as the EVM is meant to demonstrate the DSP and not the power.  And the EVM is almost $1000.

    Some standard thumbnail items, as switching frequency increases the losses for charging and discharging the gate capacitance will increase proportionally as will the VI switching losses and the DC losses through the inductor will increase proportionally with the higher RDSon too.

    Clearly we could approximate that the 0.9V curve at 500KHz is going to be slightly above the halfway point between the curves for the 0.8V and 1.0V curves at 500kHz.

  • 0 in reply to Brad
    Intellectual 700 points

    Brad-

    Thanks;

    During a recent review of my design, I was dinged for "hand wavy" thermal analysis of the UCD74120 stages.

    Essentially, using the efficiency curves available, I did as you said and interpolated a 0.9V/500 kHz efficiency to determine the losses.

    I then subtracted 2% for switching at 1000 kHz (that's the really hand wavy part) to arrive at losses for my conditions.

    Then, I subtracted out the losses I could calculate for the inductor, which then leaves the power dissipated in the UCD74120.

    I could probably get away with this better if I had some sort of equivalent to Power Dissipation Capacitance (Cpd) for the UCD74120 to help me scale the 500 kHz curves.

    If you have a suggestion about how better to estimate efficiency at 1000 kHz, please let me know.

    Thanks, Best, Steve