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OPA690: Operations at -Vs=-2V and +Vs=7V

Jejomar Ildefonso
Genius 9040 points
Part Number: OPA690
Other Parts Discussed in Thread: OPA691

Hi Team,

Our customer would like to operate the OPA690 using -Vs= -2V and +Vs= 7V. I have checked the datasheet and it seems that the positive supply exceeds the recommendations, but is still within the device's absolute rating. The main purpose is to have a proper margin in the output voltage.

Would this operating condition be suitable? Does this violate any functionality of the OPA690?

Thank you in advance.

Kind Regards,

Jejomar

  • 0
    Guru 48395 points

    as long as the total operating supply voltage (V+ - V-) is less than the AbsMax, you will be fine, I think that is 11V on this device

    There are rarely grounds in op amps so it is just the total supply voltage across the supply pins that matters. 

  • 0
    TI__Genius 17456 points

    Hi Jejomar,

    A couple of things here:

    First, what output voltage range is the customer looking for, if the margin is tight enough to exceed recommended operating conditions?

    Second, after referencing the datasheet I found the absolute maximum supply voltage to be plus or minus 6.5V, with a recommended maximum of plus or minus 6V.

    I do believe operating the positive supply pin +Vs at 7V with -Vs at -2V would not be a suitable operating condition.  Have you tried simulating the part with these supply voltages?

    Best,

    Alec

    EDIT: I see I hastily misinterpreted a value on the datasheet (and probably the essence of your question), please see Michael and Kai's responses.  I apologize for any confusion or discontinuity among responses.  Good luck with the design.

  • 0
    Guru 140200 points

    Hi Jejomar,

    figure 50 of datasheet shows that the positive supply voltage can even be +12V, provided that the total supply voltage does not exceed the recommended maximum supply voltage which is +/-6V or +12V/0V. So, +7V/-2V should be ok. But take care that the input voltage does not exceed the supply voltages. It would help, if all other stages within the signal path are also powered by +7V/-2V.

    Kai

  • 0 in reply to kai klaas69
    Guru 48395 points

    Alec's comment is incorrect, that 6.5V max is probably in the context of balanced supplies implying 13V total with +/-6.5. Your 9V total is well below the max delta across the supplies, 

    The rest of the discussion from Kai is about observing I/O headrooms which is of course always required. The I/O swings are always relative to the required headroom to the supplies, This OPA690 (the slew enhanced VFA version of the CFA OPA691) requires 1.2V headroom on the the output, and 1.6V headroom to each supply on the inputs, 

    I tried to discuss this more generally in this recent article - the first of now a 10part series heading to ?? parts. This is Insight #1 as it comes up so often, 

    https://www.planetanalog.com/author.asp?section_id=3404&doc_id=564967

  • 0 in reply to Michael Steffes
    TI__Genius 9040 points

    Hi Team,

    Thanks a lot for your help!


    Kind Regards,

    Jejomar