• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 2 answers
  • Subscribers 65 subscribers
  • Views 155 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TPS3813-Q1: Is a pulldown resistor needed on WDI pin?

Matt Calvo
Genius 13885 points
Part Number: TPS3813-Q1
Other Parts Discussed in Thread: TPS3813,

Hey Voltage Supervisor team,

I have a customer using the TPS3813-Q1 for a project and we noticed that there is a discrepancy between the TPS3813 and TPS3813-Q1 datasheets that we're hoping you can help clear up.

In the TPS3813 datasheet there are multiple sections that mention if a GPIO pin is used to drive the WDI input pin then a pulldown resistor must be added to keep the WDI pin from floating during power up. In the TPS3813-Q1 datasheet there is no mention at all of needing a pulldown resistor in any circumstance so can you please help to clarify if there is indeed a functional difference between these two devices which warrants not putting the pulldown for the -Q1 version?

Also, what happens if the WDI pin is left floating for a period of time? 

 

Best regards,

Matt Calvo

  • 0
    TI__Genius 14541 points

    Our team will answer shortly. Thank you.

  • 0
    TI__Prodigy 500 points

    Hi Matt,

    Thank you for your question!

    There is no functional difference between the -Q1 and regular variants. The -Q1 variant is tested slightly differently to meet automotive standards.

    The need for the resistor depends on the functionality of the microcontroller and its GPIO pin. If GPIO functionality is defined at bootup by the MCU and is held at a default state (0 or VDD) then there is no need for an external resistor. If the GPIO pin behavior is not defined, it is recommended to use the pulldown resistor to keep the WDI pin from floating on bootup.

    If the WDI pin is left floating, the behavior of the TPS3813 will be unpredictable since the WDI pin is not properly defined, so it is recommend keeping it well defined both on bootup and during operation.

    I hope this helps!

    Best Regards,

    Andrew Li

  • 0 in reply to Andrew Li
    TI__Genius 13885 points

    Thanks for the reply Andrew!

    I'll go ahead and pass this along to the customer and will have them comment back on this thread directly with any follow-up questions they may have.

    In order to address the discrepancies between the datasheets, it would probably be a good idea for your team to also include mentioning the potential need for a pulldown resistor on the -Q1 variant datasheet since it is not mentioned anywhere in that document.

    Best regards,

    Matt Calvo

  • 0 in reply to Matt Calvo
    TI__Prodigy 500 points

    Hi Matt,

    Thank you for the feedback! I will pass this information over to our systems team to make sure it is clear for customers in the future. 

    Please let me know if you have any further questions!

    Best Regards,

    Andrew Li