• State TI Thinks Resolved
  • Replies 5 replies
  • Answers 2 answers
  • Subscribers 62 subscribers
  • Views 45 views
  • Users 0 members are here
Support feedback
Options
Options
Related

Original question:

TPS1H000-Q1: PWM behavior - current limit and Fault pin

TPS1H000-Q1: Current limit variation

Yoshikazu Kawasaki
Intellectual 896 points
Part Number: TPS1H000-Q1


Hello,

Please let me confirm if my understanding for the current limit is correct because I looked at similar threads, but I'm not sure if my understanding is correct.

My customer's conditions

  • Holding mode
  • Rcl=1kOhm -> The expected current limit is 480mA

My customer's findings

  • It didn't hit the current limit with continuous 630mA even for >10secs
  • It hit current limit if they increased the current gradually, but it was 631mA with nFAULT=low

My understandings

If the current limit is 480mA, it has variation of +/-10% as shown below, so it will be between 432mA and 528mA.  The actual current limit is 1.5x the current limit setting which is between 648mA(=432x1.5) and 792mA(528x1.5).  The customer's case is slightly lower than 648mA, but it would be measurement error.  Is my understanding correct?  If not, would you please tell me the reason why my customer saw the higher current limit than expected?

image.png

image.png

Best Regards,

Yoshikazu Kawasaki

  • 0
    TI__Mastermind 30440 points

    Hi Kawasaki-san,

    That is correct. Once the current limit is tripped, the device will limit the current to the calculated value (480mA typ). But if the current increases slowly past the programmed current limit threshold, the current limit may only trip up to 1.5x above the programmed limit.

    Does the customer see the device limit the current to 631mA steady-state? What components do they have the DELAY pin connected to?

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Intellectual 896 points

    Hello Patrick-san,

    Thank you very much for your quick reply.

    I'm not sure if they see steady state of 631mA, but it wouldn't be.  They connect DELAY to GND directly.

    > Once the current limit is tripped, the device will limit the current to the calculated value (480mA typ).

    Do you mean if the current changes from 100mA to 500mA, for example, it will hit the current limit?  The following shows the plot I got from them, but it didn't hit the current limit.

    Best Regards,

    Yoshikazu Kawasaki

  • 0 in reply to Yoshikazu Kawasaki
    TI__Mastermind 30440 points

    Hi Kawasaki-san,

    One more point, can the customer provide a schematic? If they are using a diode/resistor ground network and the current limit resistor is connected to system ground instead of IC ground, the current limit will be shifted.

    Thanks,

    Patrick

  • 0 in reply to Patrick Shalton
    Intellectual 896 points

    Hello Patrick-san,

    I sent you friendship request.  Please accept it so that I can send you their schematic without showing in public.

    Best Regards,

    Yoshikazu Kawasaki

  • 0 in reply to Yoshikazu Kawasaki
    TI__Mastermind 30440 points

    Hi Kawasaki-san,

    I've accepted the request, let's continue via messages.

    Thanks,

    Patrick