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TPS25980: eFuse Accuracy

.
Prodigy 10 points
Part Number: TPS25980
Other Parts Discussed in Thread: TPS1663, TPS2663

Tool/software:

Hello,

we are designing a power supply unit for 24V with unknown load currents.

Since we need to comply with IEC61010-1 we want to connect two TPS25980 in series and set the current limit to the maximum possible value of 6.25A.

(9.4 b) 3) A regulating network limits also in SINGLE FAULT CONDITION)

The datasheet mentiones a accuracy for ILIM. At 6.25A the accuracy is ~11%. Is this to be understood as a deviation, so that in order to reliably limit the current to 6.25A, I have to set the limit to 5.56A?

Many thanks in advance.

  • 0
    TI__Mastermind 38335 points

    Hi!

    . said:
    The datasheet mentiones a accuracy for ILIM. At 6.25A the accuracy is ~11%. Is this to be understood as a deviation, so that in order to reliably limit the current to 6.25A, I have to set the limit to 5.56A?

    Yes, you can expect worst case variation of ~11% from the typical value of 6.25A due to Process variation and temperature variation. If you want to limit the current below 6.25A worst case, then yes, you should keep the current limit lower. Using 5.6A typical current limit should be good. Can you tell me your operating max current. We cannot keep the limit very low which might prevent the operating current in worse case. 

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 10 points

    Hello Arush,

    Thanks for the input. I will consider the deviation and set the limit lower, probalby to 5.6A.
    The max current will be 5A.

    Follow up question:
    I used the design calculator, and it looks like that with a load capacitance of 1000uF and my specs, the device will get into thermal shutdown mode.
    Since I dont really know the load resistance and capacitance this might happen.
    I dont mind if the systems needs some retrys to fully startup, but can the device take damage from going into shutdown mode?

    If the device takes damage I will probalby use the TPS1663 or TPS2663 since they seem to be more robust.

    Best Regards.

  • +1 in reply to .
    TI__Mastermind 38335 points

    Hi Kevin,

    . said:
    I used the design calculator, and it looks like that with a load capacitance of 1000uF and my specs, the device will get into thermal shutdown mode.
    Since I dont really know the load resistance and capacitance this might happen.

    If your load cap is 1000uF, then yes the device may have to go through some retries during startup.

    . said:
    I dont mind if the systems needs some retrys to fully startup, but can the device take damage from going into shutdown mode?

    No, the device won't get damaged due to this. This is a protection mechanism which prevent SOA violation of FET. 

    . said:
    If the device takes damage I will probalby use the TPS1663 or TPS2663 since they seem to be more robust.

    TPS1663 and TPS2663 can be considered since presently you will have to use TPS25980 at its max recommended voltage. This switch will provide you more margins. These two are industrial eFuses so they have very high Vin max and should be able to support 6A current. 

    Best Regards,
    Arush

  • 0 in reply to Arush Gupta
    Prodigy 10 points

    Thank you Arush, that was helpful.

  • 0 in reply to .
    TI__Mastermind 38335 points

    Happy to help :)