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  • TI Thinks Resolved

TL103WA: Op-Amp Field Failure

Part Number: TL103WA

This part is being used on a siren/microphone product. When microphone is keyed, the PA does not enable. The signal makes it to the Microcontroller but voltages across Op-Amps are zero.

Customer power source is 12 to 14 Volts (vehicle battery).  

  • Hi Bret,

    Sorry that you're having challenges with this device. Are you able to provide any more detail? From what you have provided it is quite difficult to say what might be going on. Any debugging information or schematics would be very useful.

    Best,
    Paul
  • In reply to Paul Goedeke:

    Hi Paul,

    Sorry about that, I meant to add a schematic (please see attached). I'm not an OpAmp expert so I may need some assistance with what information to provide (hope that is ok)?

    TI OpAmp Schematic.pdf

  • In reply to Bret H:

    Bret,

    Thanks for the schematic. We will look at this Monday. If you have any voltage measurements or waveforms, that would be helpful.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Ron Michallick:

    Hi Bret,

    We've looked at your schematic and getting some further information on measured voltages or waveforms will be necessary. It is unclear what you mean by "the voltages across the op amp are zero."

    Looking at your schematic, we noticed the zener from Pin 3 on U8B to ground. Can you tell us what the part number for that device is or what the Zener voltage is for that diode? That device is internal, sorry for the oversight.

    What is the gate voltage on Q10? Does it go low enough to turn off Q10?

    Thank you,
    Paul

  • In reply to Paul Goedeke:

    Bret,

    I made a mistake in my previous reply, please see my amended comments.

    Thanks,
    Paul
  • In reply to Paul Goedeke:

    Bret,

    I put your schematic into a TINA simulation using an alternate device for the Op Amps. The simulations use the LM358 which is similar in performance to the TL103WA.

    On a DC level, the circuit appears to work as desired, toggling the switch changes the output signal KEY. Perhaps you can take a look at the attached schematic and let me know if I misunderstood any part of your design and if you're able to simulate the failure that you're seeing.

    Best,

    Paul

    TL10W_FieldFailureV7.TSC

  • In reply to Paul Goedeke:

     Hi Paul,

    Thanks for the info. My apologies on the 0 volts across the OpAmp. What I meant was that the comparator reference voltage went down to 0 volts. However, after talking with our EE, he said a few of them went up to the 7.5 volt rail, when it should have been 2.5 volts.

    I have passed the information along to our electrical team, and they should have time to look at the information you have provided tomorrow. I will also ask them to provide waveforms and voltages.

    Thanks again, 

  • In reply to Bret H:

    Bret,

    If pin 3 is zero then it is accidentally shorted (solder blob) to pin 4.
    If pin 3 is 7.5V then pin 4 is accidentally open (solder gap) or measurement is not at pin 3 of TL103W

    I recommend changing R40 closer to 5k to ensure 1mA to pin 3.

    Regards,
    Ronald Michallick
    Linear Applications

    TI assumes no liability for applications assistance or customer product design. Customer is fully responsible for all design decisions and engineering with regard to its products, including decisions relating to application of TI products. By providing technical information, TI does not intend to offer or provide engineering services or advice concerning Customer's design. If Customer desires engineering services, the Customer should rely on its retained employees and consultants and/or procure engineering services from a licensed professional engineer (LPE).

     

  • In reply to Ron Michallick:

    Hey Ron and Paul,

    Thank you for the information. I received the following information from one of our electrical engineers (see attached). I hope this helps with the voltages and wave-forms you requested. Let me know if I can provide any more information.

    Thanks again, 

  • In reply to Bret H:

    Sorry, I removed the attachment as I thought this forum was private. Can I email you the report? Thanks.

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