• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 48 subscribers
  • Views 1358 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.

OPA991: Is Shutdown active-low or active-high? The datasheet contradicts itself.

Edgar Brown
Prodigy 10 points
Part Number: OPA991

On the July 2020 revision of the OPA991 family datasheet there are multiple contradictory statements about the behavior of the shutdown pin in this family. Different active high/active low statements and designations for the multiple versions. So, ignoring all the other contradictory statements for the other versions, and just looking at the OPA991S specifically:

- Figure 5-3 (which marks the shutdown pin as NC) it denotes the shutdown signal as non-inverted and indicates that shutdown is active-low.

- Section 6-3 indicates that amplifier is enabled with a high-level on the shutdown pin (i.e., shutdown is active-low)

- Section 6-7 indicates that the the amplifier is enabled with a high-level on the shutdown pin (i.e., shutdown is active-low) and consistently denotes ¬SHDN as the pin name.

- Section 7.3.11 extensively describes the functionality as if the shutdown pin is active-high. Indicating that an internal pull-down enables the amplifier if the pin is left unconnected.

Which one is it then?

Is there an errata or a more recent version of this datasheet?

  • 0
    Guru 48395 points

    well on that datasheet, page 4 there is also this for the single, not clear 

    but for the dual you get more on page 7, I think both of these are saying pulling the line low turns the part on and taking high turns it off. 

    I would guess the table 6.3 is listed backwards and the specs are very confusing, suggesting a very narrow band close to each supply for each logic level - yea this needs to some work. The discussion in section 7.3.11 clearly is active low to turn the part on and it says anything above V- + 1.2 is off

  • Former Member
    0 Former Member

    Hi Edgar,

    The online version of the data sheet should be the latest one.

    I understand where the confusion lies and am sorry for any frustration that may have been caused.

    I have forwarded the issues to the appropriate engineers and am awaiting their response.  I will get back to you ASAP.

    Regards,
    Daniel

  • 0 in reply to Former Member
    TI__Mastermind 22112 points

    Hey Edgar, 

    Obviously there is an error here, but to answer your question please reference this e2e post: 

    All the best,
    Carolina

  • 0 in reply to Caro Walter
    TI__Mastermind 22112 points

    Hey Edgar, 

    Daniel pointed out that I linked OPAX990 and you are referencing OPAX991.
    Sorry for adding to the confusion, we will update soon. 

    All the best,
    Carolina

  • Former Member
    +1 Former Member in reply to Former Member

    Hi Edgar,

    The OPAx99x devices are enabled with a logic low signal.

    I was able to get confirmation from the engineer that usually covers this part, but is currently out of the office.  I will push the engineers responsible for the data sheet to resolve this issue ASAP.

    Regards,
    Daniel

  • Former Member
    0 Former Member

    Hi Edgar,

    Hopefully this last response has answered your question.  Please let me know if you have any follow up.

    Also, thank you very much for your detailed explanation of the issue.  I have made several individuals aware of this problem and the need for improvements to the data sheet.

    Regards,
    Daniel