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OPA192: Replacement with larger Vs range

Hayden_Hast
Intellectual 1515 points
Part Number: OPA192


Hello,

I had designed the OPA192 into a circuit and it was running off of V+ = 28V and V- = -5V. However, I realized that I don't have a wide enough margin on the Vs tolerance.

Assuming 5% variance on my power rails, the max Vs = 34.65V, giving me only 1.35V of headroom until I hit 36V. This isn't acceptable for my current application.

Therefore, I wanted to see what was the closest I could get to the OPA192, but with a greater Vs. I can't seem to find any rail-to-rail precision op amps that Vs > 36V. Any ideas on what would be the next best option?

Regards,

Hayden

  • 0
    TI__Guru 68541 points

    Hayden,

    OPA192 specified power supply range is from 4.5V to 36V (+/-2.25V to +/-18V) but the Absolute Maximum Rating of OPA192 supply voltage is 40V single or +/-20V dual supply - see table 6.1 in the datasheet.  For that reason you do not need to worry about any reliability issues related to running OPA192 off 34.65V supply.

  • 0 in reply to Marek Lis
    TI__Intellectual 1515 points

    Marek,

    I'm aware that we fall well within the abs max ratings, but it's my understanding that the device won't properly operate above the 36V threshold, is that correct? I thought the device could survive if it was subjected to ~40V or so of Vs, but it wouldn't properly function.

    I've attached the circuit with the OPA192 in question (U66) below for reference.

    This is for an aerospace application so the tolerance limits are pretty strict.

    OPA192_U66_VSlimit.docx

    Regards,

    Hayden

  • 0 in reply to Hayden_Hast
    TI__Guru 68541 points

    Hayden,

    No, it is not correct to say that OPA192 will not work properly above 36V maximum SPECIFIED supply voltage of 36V - OPA192 may not meet all the datasheet limits with Vs>36V BUT this is different than saying it will not work properly because it will continue to work like an op amp.  

    However,  there is a broader point to your line of questioning about power supply variance – in your worst case analysis you have assumed 5% variation but then you go on to question if this is good enough since it leave you with just 1.35V headroom – anything greater than zero should be good enough.  The reason why you include the power supply variation in your considerations is that once you have done it and there is ANY headroom left you don't go on slippery slope of questioning whether this is good enough – you must use variance criteria based on some knowledge of the supplies and if the application meets them you should just accept it.