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DS15BR401: No connect pin for replacement DS90LV804

Satoshi
Guru 19645 points
Part Number: DS15BR401
Other Parts Discussed in Thread: DS90LV804, DS15BR400

Please let me confirm about NC pin of DS15BR401;

【Background】

・At first, customer is designing DS90LV804, but they realized that termination resister should put external.

・Most compatible and external termination resister IC is DS15BR401, but below pins are difference.

　DS90LV804　DS15BR401

　1：GND　 　　：N/C

　17：GND　　　：N/C

　18：GND　　　：N/C

　19：VDD　　　：N/C

　22：VDD　　　：N/C

・Customer is already made circuit board, they can't big change and want not NC pin left open.

【Question】

①Are these NC pin perfectly no connection from internal DS15BR401 circuit? 

②About 19pin and 22pin for DS15BR401, are these pin should connect VDD?

　I think that GND connection is no problem, is it correct?

③Just in case, are 1pin, 17pin, and 18pin connect to GND no problem?

Best regards,

Satoshi

  • 0
    TI__Mastermind 29655 points
    Hi Satoshi-san,

    I searched through our DS15BR400/401 documentation and am unable to locate specifics on these pins. Therefore, based on the datasheets alone, I would advise that the pins listed as N/C remain as N/C for proper device operation. I cannot confirm that the device will operate as expected if these N/C pins are connected to VDD or GND.

    May I ask why the device must have external terminations? One thought is that the DS90LV804 can still be used if the customer simply leaves the 100-ohm differential termination resistors unpopulated. Is this an option for your customer?

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19645 points
    Michael-san

    Thank you for reply,

    About the reason of external termination, customer is using DS15BR401 for multiple line.

    ※Image is below----------------------------------------------------------------------------------------------
    Mother board ←－－・・・－－－Termination resister－－－→ Multiple board-1
    　　　　　　　　　　　　　　　　　　　　　　　　　|
    　　　　　　　　　　　　　　　　　　　　　　　　　 －→Multiple board-2
    　　　　　　　　　　　　　　　　　　　　　　　　｜
    ----------------------------------------------------------------------------------------------------------------------

    Customer should not use internal termination because "double termination".
    　　　　　　　　　　　　　　　　　　　　　　　　　
    One customer update, 19 pin and 22 pin can change NC no problem. (DS90LV804's VDD pin)
    But 1 pin and 17 pin and 18 pin can't change NC by customer's manufacture. (DS90LV804's GND pin)
    If 1 pin and 17 pin and 18 pin can connect GND, this question is clear.

    Best regards,
    Satoshi
  • 0 in reply to Satoshi
    TI__Mastermind 43795 points

    Hi Satoshi-san,

    The pins are no connect.  They are not connected to anything inside the package.

    Regards,

    Lee