• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 387 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.

TPS3838: Tie reset output to the MR input

Xaver
Expert 8165 points
Part Number: TPS3838

Hi all,

I have one question: For the TPS3838 daisy chain, if we tie the reset output of the first TPS3838 to the next TPS3838’s MR input, do we need an external pull up resistor for this signal? Can we rely on the pull up from the second TPS3838’s MR input for the first TPS3838’s reset output signal?

Thanks a lot!

Best regards, Xaver

  • 0
    TI__Genius 12630 points
    Hi Xaver,

    I believe this will work as long as the /RESET current does not exceed ABS MAX = 5mA.

    If we take the worst case VDD of TPS3838 = 6V, we know the internal /MR pull-up resistor is 30kohm, and the /MR will consume max of 340uA

    This would produce 6V / 30kohm = 0.2mA which is lower than 5mA ABS MAX and enough to supply to /MR pin.

    Please test but I do not see any issue with this configuration. Note: this does not meet the Recommended pull-up resistor value in the Recommended Operating Conditions table on page 3 of the datasheet, as calculated by minimum R_pull-up = V_pull-up / 50uA and for VDD max = 6V, this recommends a pull-up resistor value of 120k ohm (and recommended 32kohm pull-up resistor for VDD min = 1.6V). But because this does not violate or even get close to the ABS MAX limit of 5mA, I don't see any issues.

    Let me know if you have any additional questions. Thanks!

    -Michael