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spiking noise of INA333

Shinichi Inoue
Guru 20926 points
Other Parts Discussed in Thread: INA333

Dear specialists.

My custmer is using INA333.

But some devices of the output include spiking noises.

Please teach me what kind of reason can be considered?

Could you see a attached file.
 
Best regards,
Shinichi Inoue

1205.bad operation of INA333.pdf

 

  • 0
    TI__Mastermind 25815 points

    Shinichi-san,

    Please answer questions:

    a) How many devices show this behavior?
    b) Does behavior appear on all PCBs?
    c) Attached file says there are 3 circuits. One shows behavior. Does behavior go away when 'bad' device moved to other circuit and/or PCB?
    d) What is voltage of output spike?
    e) What is time scale?
    f) Red trace is output, yellow trace is input, correct?
    g) Have you used oscilloscope to look at power supply pins and ECG_Base?

  • 0 in reply to Pete%20Semig
    Guru 20926 points

    Dear Pete

    Thank you for your reply.

    I'm sorry for the lateness, because of the lateness of customer renponse

    a)They were happened 2series of the customer model.
    b)4pcs/180pcs of the board.
    c)They hadn't confirmed the other board yet.
    d)The peak of the spiking noise is 111mV
    e)The total time is 10sec.
    f)They are used 3 circuits(boards) in product.
    They were measured 3channels at the same time.
    In the waveform of red color is bad, yellow is good.
    The other is completely the same to yellow, it couldn't see.
    g)They haven't confirm any point yet.

    Extra information is there.
    ECG BASE 2.9V is wrong, 1.4V is correct.

    I revised the attached file.

    Could you please advise me something happened at this time [View:http://e2e.ti.com/cfs-file.ashx/__key/communityserver-discussions-components-files/14/8233.bad-operation-of-INA333-20130911.pdf?

    I requested customer to confirm your indication.
    When I receive, I will feedback.

    Best regards,

    Shinichi Inoue

  • 0 in reply to Shinichi Inoue
    Guru 20926 points

    I couldn't see the file.

    I 'll attach again..

    3632.bad operation of INA333 20130911.pdf

     

  • 0 in reply to Shinichi Inoue
    TI__Guru 64840 points

    Shinichi,

    There might be a problem with customer's biasing of the bipolar transistors, Q1-Q4 (see in circles below), at the inputs of INA333.

    Q1 NPN is diode-connected with its Base at ECG BASE=1.4V and Emitter at +2.9V so it is turned-off

    Q2 PNP has its Emitter at +2.9V and its Base close to ECG BASE=1.4V so it is turned-on with its base current being dumped into INA333 IN- terminal.

    Q3 PNP diode-connected has its Emitter grounded while its base/collector is at ECG BASE=1.4V so it is turned-off.

    Q4 NPN has its Base close to ECG BASE=1.4V while its Emitter is grounded so it is turned-on with its base current being sunk from INA333 IN+ terminal.

    All these results in an asymmetrical biasing of the INA333 inputs, which may results in an unpredictable performance.  If you need further assistance, please explain reasons behind above biasing scheme.  It would be also very helpful if you could zoom-in on the waveform time-scale so we could better see the shape of the noise spikes.

  • 0 in reply to Marek Lis
    Guru 20926 points

    Dear Marek

    Thank you for your kindness reply.

    I'll confirm the purpose of Tr circuit and request zoom-in waveform.

    When I get , I'll feedback to you.

    Best regards,

    Shinichi Inoue