• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 20 subscribers
  • Views 157 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.

LSF0108: shift high level issue

Tommy Tzeng
Genius 5690 points
Part Number: LSF0108

Tool/software:

Hi Team,

may we know what is the cause? why does a low level happen on the B side when a high level of 3.3v happen on B side? thanks for your support and learn from you.

waveform and schematic as below:

PORTPROMPT_LSF0108.pdf

  • +1
    Guru 316440 points

    In the schematic, these pins are not connected to anything. But I guess that the secret device that you have not shown does not have enough drive strength to sink the current through both pull-up resistors (1.2 V / 100 Ω + 3.3 V / 499 Ω = 18.6 mA).

  • +1
    TI__Mastermind 39946 points

    Hi Tommy,

    Similarly to Clemens' response, please consult with the driver datasheet if this leakage current is acceptable. The pullup resistors at A/B side should be chosen based on desired speed/ power tradeoffs, see below formula for estimation:

    Regards,

    Jack