• State Resolved
  • Locked Locked
  • Replies 8 replies
  • Answers 3 answers
  • Subscribers 63 subscribers
  • Views 387 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS1H100-Q1: Current limit trigger and reaction time

Marco Antolovic
Prodigy 30 points
Part Number: TPS1H100-Q1

Hi all,

I´m using the TPS1H100-Q1 Ver. A. In order to estimate the variations on current limit reference I need the Min/Max voltage levels for VCL,th.

Is it possible to have it?

Also, in ca case of current limit detection, what is the reaction time between the detction and the assertion of ST to low

Many thanks,

Marco Antolovic

  • 0
    TI__Expert 4065 points

    Hi Marco,

    To your first question, there is only one Vcl,th. The way of calculating the current limit reference is by this equation: 

    Rcl= (Vcl,th * Kcl)/(Iout), where "Iout" is the target current limit, "Vcl,th" = 1.233, and "Kcl"=2000. Solve for Rcl using your target current limit.

    If your target current limit is >0.5A, +/-20% of the current limit accuracy needs to be factored in. 

    The minimum/max current limit will be:

    Imin= (0.8)(Vcl*Kcl)/(Rcl+1%*)

    Imax=(1.2)(Vcl*Kcl)/(Rcl-1%*)

    *You may need to factor in the tolerance of your resistors for calculated Rcl, typically +/-1%.

    If your target current limit is >1.6A, all of the steps are the same, but this time the factored accuracy is 14%. 

    For your second question, we don't have that spec in our datasheet so I will have to see if we have that information somewhere else and get back to you. 

    Regards,

    Krystian

  • 0 in reply to Krystian Plaskota
    Prodigy 30 points

    Hi Krystian,

    the formula you used assumes a reference voltage Vcl that is ideal.

    In reality Vcl will impact current limit as well.

    For example, let us assume the following

    1.) A variation of 5% in Vcl

    2.) A variation of 14% in Kcl

    3.) Rcl = 1kOhm

    3. No variations in resistance

    In this condition your accuracy will fall from 14% (considering only variations on Kcl) to 19.7%

    You can see the difference is significant.

    Unless threre is something that is not written in the datasheet, this is what happens.

    And this is the reason why I´m interested in the tolerance on Vcl.

    Regards,

    Marco

  • 0 in reply to Marco Antolovic
    TI__Expert 4065 points

    Hi Marco,

    You can use the datasheet value of VCL because any sort of variance that Vcl would have is already accounted for in the Kcl accuracy percentage. 

    And a follow up to your second question in your original post is that the reaction time between detection and ST to low is only a couple microseconds, 2-3us at most. We don't have a spec for this specifically. 

  • 0 in reply to Krystian Plaskota
    Prodigy 30 points

    Hi Krystian,

    thanks for clarifying variations on VCL. Please note that this is quite an inportant information and it should have been shared on the datasheet.

    With regards to the reaction time. Can you please confin that this is the absolute maximum?

    Regards,

    Marco

  • 0 in reply to Marco Antolovic
    TI__Expert 4065 points

    Hi Marco,

    Thanks for the feedback. To your second question, we are unable to guarantee an absolute maximum as it is not a specification parameter, however if it's operated within the datasheet conditions, the device will survive the short circuit event.

    Regards,

    Krystian

  • 0 in reply to Krystian Plaskota
    Prodigy 30 points

    Hi Krystian,

    to clarify, are you saying that there is no known upper limit on the time interval required by the ST to go low?

  • 0 in reply to Marco Antolovic
    TI__Expert 4065 points

    Hi Marco,

    As it is only a few microseconds we consider this real time and subsequently do not spec the parameter.

    Regards,

    Krystian

  • +1 in reply to Krystian Plaskota
    Prodigy 30 points

    The concept of real time is relative, if you need nano seconds you will have a problem (not that it will happen here...).

    In any case, I will take 3us as typical value and report no upper limit available.

    I have to say it is surprising that a theoretical max limit can´t be provided for a fault detection pin on an automotive grade component.

    Regards,

    Marco