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Stress calculation on TPS5430 application

Hidekazu Someno
Expert 5130 points
Other Parts Discussed in Thread: TPS5430

On TPS5430 application  circuitry, The calculated SBD(D1) dissipation is showed on STRESS screen. But that power dissipation is not correct, I think.

My conditions for the application are; VIN=11V-13V(typ=12V), VO=3.3V, IO=3A.  On the default application created based on that conditions, D1(catch diode)'s dissiopation was 202mW at 2.59A RMS current.  It means Vf of D1 is about 80mV. too low.  The calculation should be corrected, I think.

  • TI__Intellectual 1280 points

    Thanks for the feedback.

    We found this bug early last week.  Looks like our conduction loss was wrong.  For Conduction loss we were using Vdiode*RMScurrent*DutyCycle.  So it appears we were double dipping on the duty cycle since RMS current already has duty cycle factored in.  So we've removed the extra duty cycle term and it appears to be correct now.  We'll be updating the software in production tomorrow around noon (central time)

     

  • in reply to Heath Gallimore
    TI__Intellectual 1280 points

    This is fixed in production now.  The same design above gives me 642mW of Power Loss on the D1 catch diode.  That's about 0.25 vF on the diode, much closer to reality.