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TPS2553/about IOS

Tsukui Yusuke
Guru 21930 points
Other Parts Discussed in Thread: TPS2553

Hi,

Could you tell me about TPS2553 programming the current-Limit?
Calculation result are different from Table2.
What is the difference?

TPS2553 about Ilim.pdf

Could you give me your advice?

Best regards,
Yusuke/Japan Disty

  • 0
    TI__Expert 3995 points
    Hi Yusuke,
    Thank you for bringing this to our attention, your calculation for current limits are accurate and will be working on to update the datasheet with the corrected calculations.

    Best,
    Haidar,

    Please consider checking the "Verify Answer" button if I've answered your question.
  • 0 in reply to Haidar Hamoo
    TI__Expert 3995 points
    Hi Yusuke,
    Just wanted to explain the difference in Ios calculations you saw in TPS2553 datasheet compare to the calculation you did. Datasheet Ios calculations took in account 3 decimal places in calculating resistance value tolerance (the 1% low and 1% High) then applied this calculated values in the Ios (min, nom, and max equations) to get current limit you saw on the datasheet, so as an example:
    RILIM (closest to 1% ) = 16.9 kohms will produce (16.731 k ohms 1% low) and ( 17.069 k ohms 1% High), thus giving Ios(max) = 1626.4 mA, Ios(Nom) = 1512.4 mA, and Ios(Min) = 1412.5 mA which are the values you saw in the datasheet for this resistor.
    On the other hand, your calculation for the same resistor value followed a more accurate and conservative way of calculating Ios(Min), Ios(Nom), and Ios (Max) and that's why I wanted to follow-up and explain the difference you saw.
    Again thank you very much for bringing the issue to our attention.
    Best,
    Haidar
  • 0 in reply to Haidar Hamoo
    Guru 21930 points

    Haidar-san,

    Thank you for your detail description.
    I understood your description.

    Let me ask you one more thing.
    Is this expression affected by the temperature?
    If the effect,
    Please tell me the correction formula.



    Best regards,
    Yusuke/Japan Disty

  • 0 in reply to Tsukui Yusuke
    TI__Expert 3995 points

    Hi Yusuke,

    Current limit threshold expression will be affected by temperature as mush as RILIM value is affected by this temperature and that's why we recommend 1% RILIM resistor to be used in order to ensure stability within the internal regulation loop, but the current limit threshold expressions used in TPS2553 datasheet account for current tolerance due to variation caused by temperature and process and no need for correction as long as the device is operating within the recommended operation conditions.

    Best,

    Haidar

    Please consider checking the "Verify Answer" button if I've answered your question.