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OPA2182: overconsumption

ziad jabbour
Prodigy 100 points
Part Number: OPA2182
Other Parts Discussed in Thread: OPA2350, OPA2187, OPA2189

hello we use the OP2182 as a buffer for the reference voltage 

the amplifier is overheating to 85°C we check the power consumption it is 58mA, to be known that the component power tow reference circuit 

for TX : 

For RX : 

We desolder the component while powering the output (pin 1 and 7) via a power supply to emulate its present we have 1,5mA output current consumption 

we tryed to power the OPA2182 via external power supply (pin 8), we noticed that when the opa is powered at 6,8V it is consuming 3,5mA when it is powered at 6,9V it consumes 40mA, in both cases the output is 5V

I noticed that the ref on the component is : OP2182

please can you help us with the root cause to solve the issue 

best regards

Ziad

  • 0
    TI__Guru 68991 points

    Ziad,

    First, OPA2182 like almost all other amplifiers will oscillate with uF loads, which could push it into short-circuit conditions (typical 65mA) and heat up the package.

    Also, what you describe in terms of IQ of 3.5mA is twice what OPA2182 (dual) should be under quiescent conditions ( 2* 0.85mA) - see below.

    Please remove all the output cap loads and test the circuit again. 

  • 0 in reply to Marek Lis
    Prodigy 100 points

    Hello Marek, I confim once all capacitor are remooved the over consumption disapear 

    do you recomand another opamp that can solve the issue 

    since the output power the referece circuits 

    next time i will not reference my reference voltage, i will use the reference directly 

    best regards

  • 0 in reply to ziad jabbour
    TI__Guru 68991 points

    Only OPA2350 can directly drive 22uF load but its offset and temperature drift is not as good as OPA2182.  

    You may stabilize OPA2182 by adding 20ohm series output resistor - see below  - which meets the recommended max overshoot of 25%.

    However, if the output of the buffer drives a resistive load, the 20ohm series resistor outside the loop would cause Vref error due to voltage divider. 

    In such case you would need to use a dual-feedback configuration as shown below.

    OPA182 dual feedback.TSC

  • 0 in reply to Marek Lis
    Prodigy 100 points

    Thanks Marek, my circuit is drived via +15V, the OPA2350 is limited to 5V, do you have a solution with +15V

    is the de OPA2187IDR or  OPA2189IDR can deal with the situation ? 

    best regards

  • 0 in reply to ziad jabbour
    Prodigy 100 points

    by the way the ref voltage is a 5 delivered by a reference circuit from TI, not a square wave, 

  • 0 in reply to ziad jabbour
    TI__Guru 68991 points

    There is no high voltage op amps capable of direct driving 22uF loads - not OPA2187, OPA2189 nor OPA2xxx can handle such load. 

    Above I already  provided you with two solutions.  Square wave is ONLY there to check the stability by looking at the small-signal overshoot.