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OPA4990: POR

Oba
Genius 15750 points
Part Number: OPA4990
Other Parts Discussed in Thread: OPA4197, OPA2990

Hello

Does OPA4990 have POR?
My customer wants to use an OpAmp that doesn't have POR to avoid inrush current at POR release timing.

Regards,
Oba

  • 0
    TI__Mastermind 20750 points

    Hi Oba,

    Let me take a look into this to see! 

    Best Regards,

    Robert Clifton 

  • 0
    TI__Guru*** 139906 points

    Hello Oba,

    How fast will the power supply rise? Is there a limit to peak IQ that would be acceptable? 

  • 0 in reply to Ron Michallick
    TI__Genius 15750 points

    Hello,

    I'm not sure about the supply rise, but they had a POR inrush current problem with OPA4197 before.
    They put about 10 opamps on the same board at the time.
    When OPAx197 POR was released, over 20mA inrush current flowed and voltage drop occurred.
    They want to avoid the similar problem and want to check if OPA4990 has POR or not.

    If OPA4990 has POR circuit, is there any other part number that is similar specification?
    They need Rail-to-rail input.

    Regards,
    Oba 

  • +1 in reply to Oba
    TI__Guru*** 139906 points

    Hello Oba,

    By lab observations with OPA2990, I learned that OPA4990 has an under voltage lock out where output is high impedance until Vs rises to about 2.1V using a very slow ramp.  For very fast ramp to 5V, the output didn't follow the inputs until time is 55us ; the output was an arbitrary voltage (not  high-Z).

    With variable rise time to 15V, I monitored IQ. The largest IQ peak occurred when rise time was 60us. This highest peak was 1mA (for OPA2990) so expect 2mA for OPA4990.  With faster and slower ramps, IQ peak was less; 10us was 0.38mA peak, 200us was 0.58mA. I would not call this POR because output was arbitrary opposed to VOL that usually happens in POR.

    Will the application create output voltage that reaches VOL or VOH? I ask because leaving VOL or VOH can cause IQ peaks in some op amps. I will ask again, How fast will the power supply rise (and to what voltage level)? Is there a limit to peak IQ that would be acceptable? 

  • 0 in reply to Ron Michallick
    TI__Genius 15750 points

    Hello Ron,

    Thanks for your lab work. It is very helpful.
    2mA is acceptable. Their power supply rise is about 15ms for 0V to 5V.

    Regards,
    Oba