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TPS25926: OCP question

Part Number: TPS25926

Hi Sir 

Due to we meet a 13A inrush current

May I know TPS25926 can support bigger current limit (modify RILIM value bigger than 150kohm)?

or disable current limit function ?

Thanks

  • Hi Kai Hsiao,

    The recommended max. RILIM value is 162kohm. Can you share your system requirements and schematic. Can you also provide description for the shared test waveform.

    Best Regards,
    Rakesh
  • HI Rakesh 

    When I use "Ultrastar SN200" this SSD on CN1 will meet inrush issue (schematic as below)

    When C121 pop ,the inrush current will be 13.08A and +12V1 will be drop to 9.484V

    When C121 non-pop ,the inrush current will be 2.4A and +12V1 will be drop to 7.192V

    May I know 

    1. Do you have any idea why this inrush current is so big?

    2. Due to we don't want to cause TPS25296 to current protection ,what's value of C121 is suitable?

  • HI Rakesh

    Below is SN200 SPEC

    If you have any suggestion ,please kindly let me know 

  • Hi Kai Hsiao,

    Thanks for more details.
    In the test waveforms - what does yellow and blue color trace corresponds to ? Is it the input voltage +12V of U52?
    Are you hot-plugging "Ultrastar SN200" SSD on CN1 connector after +12V1 becomes stable?
    How are you generating +5V and +12V supply rails?

    Best Regards,
    Rakesh
  • HI Rakesh

    CH Yellow: Close to PSU +12V Net Voltage (power supply for Backplane)

    CH Green: NC U52 measuring + 12V to + 12_1 current

    CH Blue: C67 that +12V Net Voltage (Before the eFuse)

    CH Pink: C121 that +12V1 Net Voltage (behind the eFuse)

    When We follow SN200 SPEC and change C121 from 22uF to 4.7uF 

    Inrush current still have 11.2A

    Inrush current happened on re-plug condition

  • Hi Kai Hsiao,

    When "Ultrastar SN200" SSD is inserted on live +12V1 bus, eFuse limits the current to max 5.2A (corresponding to Rilim 150kohm). It looks strange to see both input voltage +12V, PSU +12V Net Voltage (power supply for Backplane) dropping. Is this repeating on all of your boards?

    how does the system (along with SN200) behaving when you toggle "Drive_OFF_NO" signal? Have you tested SN200 module by separately powering it from 12V DC source - how is the inrush current profile ?

    Best Regards,
    Rakesh
  • Hi Kai Hsiao,

    Would like to know if you have more test results to analyse.
    "how does the system (along with SN200) behaving when you toggle "Drive_OFF_NO" signal? Have you tested SN200 module by separately powering it from 12V DC source - how is the inrush current profile ?"


    Best Regards,
    Rakesh