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TPS27S100: The behavior at fast-trip and closed loop

Michiaki Tanii
Expert 4550 points
Part Number: TPS27S100

Hi team,

 

Could you kindly advise the behavior of the below ?

 

-       After the fast trip triggered, the period until turn-on FET

-       In the case of repeating of the behavior of fast trip(several ten times or several hundred times), is there possible to shutdown not to do retry operation.

-       The response time at closed loop.

 

Thank you and best regards,

Michiaki

  • 0
    TI__Mastermind 26380 points

    Hello, 

    Thanks for posting to E2E. 

    Could you give us some additional information on the conditions under which the trip occurs;

    For example when the hard short to ground fault occurs - is there a micro controller in the system that is monitoring the Short to ground condition and turning off the TPS27S100 on fault detection? Without this; the device could continue to stay in cycles of thermal shutdown as long as the fault condition is present. 

    Also what type of load is the high side switch driving? 

    Thank you in advance for the added insight! 

    -Priya

  • 0 in reply to Priya Thanigai
    TI__Mastermind 27375 points

    Michiaki-san,

    The fast-trip response time is less than 1 μs typically. This is the case where there device is already running and the current limit condition happens. If you are turning on into a short then the regular slew rate and turn on delays apply. There is not integrated way to stop the device after a certain number of retries. The best way to do this would be to connect the FLT line to your microcontroller and have a timer/counter in software that would disable the switch after so many current limit conditions occur. 

  • 0 in reply to Timothy Logan
    TI__Expert 4550 points

    Hello

     

    Thank you for your reply.

     

    Customer would like to use the any cases as standard products, so they just want to make sure the inquiries.

     

    -       After the fast trip triggered, the period until restart to turn-on FET

    -       The behavior in the case of repeating fast-trip

    -       The response time at closed loop (not fast-trip mode)

     

    Regarding your answer, please let me confirm them

    -       Even if fast-trip behavior is repeated, TPS27S100 cannot be shut down and thermal shutdown will be continued with ILIM(TSD) of 5A

     

    I would much appreciate if you will answer the remaining 2 items.

     

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Mastermind 23220 points

    Hi Michiaki,

    That is correct, the device cannot be controlled to shutdown after retries unless disabeled. If thermal shutdown is continued, the current limit will be 5A if not externall programmed (otherwise, it would be 50%). 

    Just to clarify on your other questions

    • Are you referring to reffering to the period after the current draw from the load returns to normal?
    • By repeating fast-trip do you mean entering and exiting fast-trip?

  • 0 in reply to Anthony P Pham
    TI__Expert 4550 points

    Hi Anthony,

     

    Customer would like to make sure on the following.

     

    -       The period between the detection of fast-trip by hard short and turning on FET.
    If it is specified, please let me know.
    Regarding thermal swing and thermal shutdown, retry time would be decided by the relation of Tj

    -       The response time if current limit block diagram is operated(closed loop operation) not fast-trip function.
    It is not specified unlike the eFuse.
    Why isn’t it specified ?

     

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Mastermind 23220 points

    Hi Michiaki,

    The retry timing is designed to maintain the robust short circuit protection while maintaining current overshoot. It is not specified.

  • 0 in reply to Anthony P Pham
    TI__Expert 4550 points

    Hi Anthony,

     

    Customer has two questions.

     

    One is “the time between the detection of fast-trip by hard short and turning off FET.

    And your answer of the below is for it in my understanding.

     

    The retry timing is designed to maintain the robust short circuit protection while maintaining current overshoot. It is not specified.

     

    Another one is the response time of closed loop operation. It means not fast-trip mode but the response time by ILIM.

    Why is the response time specified in the datasheet like eFuse ?

     

    Please kindly advise the response time and the reason why it is not specified in the datasheet.

     

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Mastermind 23220 points

    Hi Michiaki,

    The closed loop response time is typically less than 1us.

  • 0 in reply to Anthony P Pham
    TI__Expert 4550 points

    Hi Anthony,

     

    Is it true that the response time is same with both fast-trip and closed loop ?

    I feel the closed loop has some delay compared to fast-trip seeing the below block diagram though…

    Thank you and best regards,

    Michiaki

  • 0 in reply to Michiaki Tanii
    TI__Genius 12410 points

    Hello,

    Are you asking this to determine if you have soft short events if the device will be able to respond to a small change in impedance?

    The big difference is that this is not an eFuse it is a high side switch which is made for rapid changes in impedance

    This current limit architecture is defined to be valid with the load current is trying to pull greater than 1.5x the current limit as would be the case in a hard short or a capacitive inrush event.

    During this time there will some overshoot but we do not spec that value because it will differ based on the load.

    For fast trip response we turn off in 1us and then immediately come back on but we are powering into a short circuit event so the slew rate is valid and the over shoot will be minimal.

    Please feel free to give an email to my self c-phillips@ti.com or Anthony a-pham@ti.com if you would like.