• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 4 answers
  • Subscribers 33 subscribers
  • Views 2637 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.

TPS2553D: Short Circuit and Over Current protect

Tamio Yokokura
Expert 3980 points
Part Number: TPS2553D
Other Parts Discussed in Thread: TPS2069C, TPS25810, TPS2553

Hi, Support team

The below is a sequence of short circuit and over current limit protection I created.

I have soome question as follows,

[1] As far as I see the datasheet, I understand that the internal FET switch is tuned off when the short circuit is detected due to the inrush current.

     How does TPS2553D identify the short circuit and over current condition ?

[2] What is the period that the internal FET turns off? and Is the period the Fixed or Variable?

[3] Is the deglitch time for /FAULT reset when the internal FET is tuened off?

Thanks!

Tamio

  • 0
    TI__Expert 8420 points
    Hi ,
    [1] As far as I see the datasheet, I understand that the internal FET switch is tuned off when the short circuit is detected due to the inrush current.

    How does TPS2553D identify the short circuit and over current condition ?
    [Answer]: TPS2553D will not identify the short circuit and over current , internal FET just sense the current through from In to out . As the inrush current is very big so after the pike spike internal will turn off and waiting for some time then restart and limit the output current. The turn off is the output short respone behavior .

    [2] What is the period that the internal FET turns off? and Is the period the Fixed or Variable?
    [Answer]: It is variable depend on input and output voltage .

    [3] Is the deglitch time for /FAULT reset when the internal FET is tuened off?
    [Answer]: the deglitch time is start from current limit threshould after internal mosfet return on ( not from the first spike )
  • 0 in reply to Michael Tan
    TI__Expert 3980 points

    The below is some question from our customer.

    [1] Why is there a delay timer until the internal FET switch is turned on from turn-off due to the inrush current at hot plug? 

    [2] When USB memory stick(SDCZ80-032G : Sandisk) is done a hot-plug, PC can NOT identify it.

          Because the internal FET switch is turned off due to inrush current and the output voltage is clamped to 1.8V as following picture.

          This is an indifinite voltage for USB Memory Stick of Sandisk. Therefore, it can not initialize correctly.

          Are there any workaround to solve this issue?

    By the way, is USB standard considered about the above issue?

    Thanks

    Tamio

  • 0 in reply to Tamio Yokokura
    TI__Expert 8420 points
    Hi Tamio-san,
    For your question pls. see below commnet :
    [1] Why is there a delay timer until the internal FET switch is turned on from turn-off due to the inrush current at hot plug?
    [Answer]: for the hot plug in , it most like hot short behavior ( sanddisk input cap is big ) ! During the hot short the a very fast and large input current go through the device internal , it will make the internal sense amplier restart ,so you can see the 1-2uS spike current during hot short .
    [2] When USB memory stick(SDCZ80-032G : Sandisk) is done a hot-plug, PC can NOT identify it?
    [Answer]: Because of our device response time is very fast , it will limit the output current during sandisk stick pulg in , that will cause the output voltage drop below the USB stick UVLO. Is this application can accepte fix current limited device tps2069C? the tps2069C device current limited response will be more lower , can you try to use this part for your design .
  • 0 in reply to Michael Tan
    TI__Expert 3980 points
    Hi, Tan

    Thank you for quick reply.
    According to customer evaluation report, the hot-plug issue occur in TPS2553D, not TPS2069C. And also, it occur in TPS25810 which other person supports.
    I duplicated using TPS2553DEVM due to I contacted 10uF MLCC to output termina on EVM under hot plug.
    Do you think that 10uF MLCC is very big as input capacitor of UFP device?
    As far as I see USB2.0/3.1 specification, 10uF is in range of specfication.

    By the way, how much is the current when the internal FET switch is turned off? I do not mind it with a design value.

    Thanks
    Tamio
  • 0 in reply to Tamio Yokokura
    TI__Expert 8420 points
    Hi Tamio,
    10 uF input cap is not big, I am warry the USB stick is more bigger than this value . We don't have the internal FET switch turn off value , as it depend on how high the di/dt it is .
  • 0 in reply to Tamio Yokokura
    TI__Expert 8420 points
    Hi Tamio,

    You can also try to use the bigger cap in the tps2553 output , more cap value it can little the Vout drop .