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DS90UB933-Q1: DS90UB933 port capacitance at data input from image sensor

Kazuki Kuramochi
Expert 8330 points
Part Number: DS90UB933-Q1

Hello Expert,

My customer would like to know about following pin's capacitance.

  • PCLK
  • HSYNC
  • VSYNC
  • DIN[0:11]

GPO and I2S's pin has capacitance information but above pins don't have such a information on datasheet.
Then, would you provide those information.

Thank you and best regards,
Kazuki Kuramochi

  • 0
    TI__Genius 11330 points

    Hi Kuramochi-san,

    Thanks for your inquiry. As you found in the datasheet we do not specify the pin capacitance of the pins which you listed. Are you looking for a method to simulate the I/O behavior of the DS90UB933? If so, I would recommend taking a look at the IBIS model for this device which is included in the product page on TI.com. 

    Best,

    Thomas

  • 0 in reply to Thomas Bejin
    TI__Expert 8330 points

    Hi Thomas-san,

    Thank you for your reply.
    I understand you suggest them to use IBIS model to confirm signal integrity.

    But pin capacitance is better to roughly estimation.
    Then do you provide roughly estimated capacitance for each pin from the point of view of IC design?
    We don't require guaranty for this answer and we'd like to know it for reference only.

    Sorry for bothering you but I'm waiting your answer.

    Thank you and best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Genius 11330 points

    Hi Kumamochi-san,

    After looking into this a bit more we do not have pin capacitance values available for the DS90BU933. The best alternative which we could provide is the IBIS model for I/O simulation.

    Best,

    Thomas

  • 0 in reply to Thomas Bejin
    TI__Expert 8330 points

    Hi Thomas-san,

    I broke down IBIS model on TI.com.
    Then pkg and those pin's capacitance is as follows.

    pkg = 0pF
    DIN[0,1] = 1.107pF(typ)
    DIN[2:11] / HSYNC / VSYNC = 1.615pF(typ)
    PCLK = 1.615pF(typ)

    Then could I regard that those pin's capacitance is as input capacitance as reference?

    Thank you and best regards,
    Kazuki Kuramochi

  • 0 in reply to Kazuki Kuramochi
    TI__Genius 11330 points

    Hi Kuramochi-san,

    We looked at the c_comp values which are included in the IBIS model as well, however the this is only one component of the total input capacitance. C_pkg is another contributing factor, however this field is listed as 0 in the IBIS model. 

    If you look at the DS90UB933 datasheet, the pin capacitance of GPIO[3:0] pins is listed as 1.5pF, however in the IBIS IO_DATA_50_ATP_HS50 model the c_comp list listed as 1.107pF. As can be seen in the case of the GPIO pins, we shouldn't assume that c_comp is the same as pin capacitance for the pins which you're looking for above.

    Best,

    Thomas

  • 0 in reply to Thomas Bejin
    TI__Expert 8330 points

    Thomas-san,

    I understand that IBIS model is using just 1 sample and it has difference against datasheet's value.
    However, you suggested to use IBIS model to estimate impact from input capacitance.
    So I'll explain them about they can use IBIS model's capacitance as just reference but it probably have gap against actual value so we cannot guaranty any result from using IBIS model's capacitance.

    Thank you and best regards,
    Kazuki Kuramochi

  • +1 in reply to Kazuki Kuramochi
    TI__Guru* 98475 points

    Hello Kazuki,

    Your understanding is correct 

    Thanks,

    Casey