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Tps54620 inductor selection

Mike Ulrich
Expert 3110 points
Other Parts Discussed in Thread: TPS54620

Hi,

When selecting an inductor for this device, does the saturation level need to be above 11A since the current limit is not adjustable?

Is there an issue with saturation point of 4a for a 1A rail?

  • 0
    TI__Guru**** 191445 points
    All depends on how you want to address fault conditions. If you expect to have frequent shorted output, you may want a higher current rated inductor. Alternately, you could look at TP54623 which has hiccup mode current limit.
  • 0 in reply to JohnTucker
    TI__Expert 3110 points
    Hi John,

    Would the inductor really cause any harm if it saturates briefly on a short circuit condition? The TPS54620 should still react appropriately and shut itself down due to OCP.

    Thank You,
    Mike Ulrich
  • 0 in reply to Mike Ulrich
    TI__Guru**** 191445 points

    TPS54620 is cycle by cycle only.  The device will keep switching, probably at minimum on time and near zero volts out, but the current will be at he maximum.  As the inductor saturates, the p-p ripple current will increase a lot.  Most modern inductors have a rather soft saturation profile, unlike some coils where the inductance would rapidly fall to near zero.  You probably just need to check the specific inductor you are considering.  Don't forget the heating current.  You may find that the inductor gets hot enough to flow the solder and fall off the PCB (ask me how I know about this).