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OPA2333: Temperature variation - at hot (120F)

Jeff Coletti
Expert 8755 points
Part Number: OPA2333
Other Parts Discussed in Thread: , INA152

Hi All

Need some help with a circuit. Attached file shows schematic. temp profile and output. What we are seeing is at around time 4hrs and when the temp is elevated to 120F the output rises. The circuit has the bridge mounted external to the temp chamber, only the amp and xtr are in the chamber. Expectation is that the output should stay at 4mA for the entire test. This product has been shipping for quite some time now (8 yrs). From the test you can see they have 16 boards failing here. they are doing another test with 14 more boards.

Customer tried replacing opa2333 one board and issue went away. Plan is to change the opa2333 on five more failed boards and verify if it tracks the op amp. If it does, next step is to re-mount 3 of the failed devices, retest, to see if it was a manufactureing issue or a part issue. If a part issue we will need a FMA.

Any other thoughts on this problem or suggestions on where to look or tests to try?

Thanks

Jeff Colettiopa2333xtr106ckt.pptx

  • 0
    Prodigy 20 points

    Hi all,

    I use the OPA2333AMDREP amplifier as the figure 8 of the OPA2333A-EP datasheet with the INA152 (R1=200Ω, R2=22kΩ) and after, the instrumentation amplifier output is amplified by 5.

    I have done some thermal tests between -40°C (-40°F) and +70°C (158°F), and around +67°C (152°C), a white noise appears and the amplitude increase exponentially with the temperature. At 70°C (158°F), the amplitude can reach more than 150mV instead of some mv on others PCBA.

    I found that the noise come from the first stage with the OPA2333AMDREP amplifier output, with a noise of 30mV (confirm the 150mV with the gain of 5). The datalogger time step is 100ms.

    The instrumentation amplifier block is powered with 5V voltage reference (stable, no noise) and is connected to a 1000Ω Wheatstone bridge with a 2.5V common mode. I short-circuited the V1 (-In) and V2 (+In) of the figure 8, verified that I have no noise on the inputs (<1µV), and measured the OPA2333AMDREP amplifier output. I have the same white noise with an amplitude of 30 mV.
    I removed the INA152 and the R1 gain resistor to have 2 followers amplifiers with 22kΩ on the feedback, and I observe on the B channel a white noise with an amplitude of 30mV.

    I replace the OPA2333AMDREP amplifier (from the same datecode 1344 or 1414) and the noise disappear.

    I put the “defective” amplifier on another PCBA and the amplifier has the same behavior (noise of 30mV).

    I change the feedback resistor from 22kΩ to 0Ω and the noise fall to 3µV.

    I add different capacitors (22µF and/or 100nF) on the feedback and I have the same noise amplitude (30mV) but slower.

    Jeff, maybe you have the same noise issue. A solution could be to reduce the feedback impedance.

    I need to know if this noise is due to the OPA2333AMDREP design and if the temperature is always around 70°C (158°F)

     

    Thanks,

  • 0 in reply to Ludovic SERY
    TI__Guru 68541 points

    We had a double clocking issue with some OPA2333 wafer lots and have made a silicon revision to fix it.  Please provide the datecodes for the suspect parts so we can confirm whether they come from the affected lots.  

  • 0 in reply to Marek Lis
    Prodigy 20 points
    Hi,

    Thank you for your response.
    The Lot number is 4411405M14 (date code 1414) or 625058ML3 (date code 1344)
    The marking on the component is 44K.

    Did you know if this oscillation is always around the same hot temperature, or it can happends at low temeprature ?

    Regards,
  • 0 in reply to Ludovic SERY
    TI__Guru 68541 points
    Yes, the above date codes indicate that they may have come from problematic wafer lots. This is a chopper double-clocking issue and not an oscillation and we have seen it between 25C to 50C ambient temperature range. Please contact directly Joe at our quality department to remedy the problem-here is his email address: j-serritella@ti.com