• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 20 subscribers
  • Views 450 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.

Original question:

TXB0302: Can the two channels support I2C 400K conversion at the same time？

TXB0302: why TXB0302 can't use for open drain case

weilun luo
Prodigy 30 points
Part Number: TXB0302
Other Parts Discussed in Thread: TXS0102, LSF0102

Could you explain why TXB0302 can't use for open drain case?

Could you show me the fail case?

  • 0
    TI__Mastermind 41596 points

    Hey Weilun,

    The TXB device series will not support open drain cases because there is a series resistor at the output that assists with the auto-direction sensing circuitry. For this same reason, we suggest that if external pullup resistors are to be used with this device, they must be >20kOhms to not contend with the output drivers of this device (hence not suitable for open drain use cases). 

    See the LSF0102 or the TXS0102 for level translation with open drain applications.


    Regards,

    Jack 

  • 0 in reply to Jack Guan
    Prodigy 30 points

    If I use pull up resistor like 9KOhm, what do you concern beside VOL and VOH?

  • 0 in reply to weilun luo
    TI__Mastermind 41596 points

    Hey Weilun,

    If a 9kohm pullup resistor was used, the VOH would not be impacted- but the VOL will become a voltage divider with the internal 1kohm and could contend with the output drivers of the TXB0302 since it fails to meet the requirement of >20Kohms. 

    If your application requires external pullup resistors on the I2C data line, I recommend taking a look at the TXS0102 (has internal 10k pullups that can be used so you would not need the 9kOhms). 

    Thanks,

    Jack 

  • 0 in reply to Jack Guan
    Prodigy 30 points

    I''m sorry.  I am focusing on the problem beside VOH and VOL.

    Do you have any idea? Thank you very much. 

  • +1 in reply to weilun luo
    TI__Mastermind 41596 points

    Hey Weilun,

    Using external pullups less than 20kohms with this device primarily impacts VOH and VOL- no other concern comes to my mind at the moment. 

    If you are satisfied with the open drain signals while using the 9kohms and on this device, then it is at your discretion. We just generally recommend TXS/ LSF devices for open drain signals.

    Regards,

    Jack