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TPS1H000-Q1: Current limit operation

Hirotaka Matsumoto
Guru 27585 points
Part Number: TPS1H000-Q1

Hi all

Would you mind if we ask TPS1H000-Q1?

Our customer uses TPS1H000-Q1 with follow condtions;
-Vin=24V
-Iout=0.65A(this is the value which the customer would like to limit.)
-CL resistor(current limit resistor) = 750ohm ± 1%
They calculated RCL value using "RCL=VCL×KCL / 0.65A".

And then, they measured limit level.
The result was 750mA.
Even though it contains tolerace of resistor(±1%) and current accuracy(±10%), we assume that maximum current limit will be 711mA.
So, we would like to the difference between customer's calculation value and measurement result.
Could you let us know follows;

<Question1>
We would like to know external current limit accuracy correctly.
So, dose it mean followings?
①0.05≦Ilimit≦0.15＠Vvs-Vout≦2.5V：±20%
②0.15≦Ilimit≦0.30＠Vvs-Vout≦2.5V：±15%
③0.30≦Ilimit≦1＠Vvs-Vout≦2.5V　 ：±10%
Is it correct? And in case of customer's configuration, will the tolerance be pattern ③?

<Question2>
In relation to <Question1>, there is formula "RCL=VCL×KCL / Iout" on the datasheet P11.
VCL and KCL show only typical value.
So, we assume that the tolerance might be ±20% nevertheless of Ilimit.

<Question3>
There is the description of Isc(Short-circuit current limit), could you let us know it?
Is operating condition Vout=0?

Kind regards,

Hirotaka Matsumoto

  • 0
    TI__Genius 12410 points

    Hello,

    I will look into this and get back to you.

    Could you please send me a schematic snippet and confirm the parts on the board through the part marking?

  • 0 in reply to Cameron Phillips
    TI__Genius 12410 points

    Hello,

    What is your typical and maximum load limit? Are you trying to run your load at 650mA and set the current limit to the same spot?

    I believe what is happening is that your max load is where you are trying to limit the current but the current limit should be higher than your maximum load and then there is some overshoot and then it clamps back to the limit of where you set it.

    This picture describes what I am talking about. Let me know if this answers your question.

  • 0 in reply to Cameron Phillips
    Guru 27585 points

    Cameron san

    Thank you for your reply.

    What is your typical and maximum load limit?
    ->Typical load limit is 650mA.

    And then, we assume that this device has two thresholds which are "over shoot" and "over load".
    Over shoot : Overshoot up to 50% of upper Limit  Ilim x (1 + 15%)x(1+50%) -> 0.625×1.15×1.5 = 1.078A
    We got "Over shoot" and it clamps back to the limit of where we set it.

    However, we could not understand "Over load" correctly.
    We recognize that "Over load" means the clamp current.
    Is it correct?
    How much is the tolerance?  Typical load limit × 1.2? or 1.3?

    Customer's mesurement result of clamp current was 750mA.
    So, actual result=750mA / Typical load limit = 650mA -> 15%, is it approxy ±15%? 
    We could not find it on the datasheet.

    Kind regards,

    Hirotaka Matsumoto

  • 0 in reply to Hirotaka Matsumoto
    TI__Genius 12410 points
    Hello,
    Could you please provide a waveform of the event that you are referring to? I do not understand how you are differentiating over shoot and over load. Are you saying that the current goes up to 750mA and then clamps back down to 650mA? If so that is the intended way and aligns with what the datasheet says of up to 1.5x the current limit.
  • 0 in reply to Cameron Phillips
    Guru 27585 points

    Cameron san

    Thank you for your support.

    We sent detail information directly.

    Kind regards,

    Hirotaka Matsumoto