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LME49860: Noise Issue

Sadanori Kato
Guru 36490 points
Part Number: LME49860
Other Parts Discussed in Thread: LME49720

Hi,

Our customer is faced with the noise issue for LME49860.
Then, there is a difference of about 9dB when comparing the noise characteristics of non-defective products and defective products with the same pcb.
Is there possibility of the popcorn noise as the root cause ?
In addition, can the popcorn noise be measured and detected accurately with the automatic test equipment(ATE) ?

This product is in mass production soon, so could you please tell me how to improve this issue ?

Best regards,
Kato

  • 0
    Prodigy 170 points

    At a guess if you are getting some parts that are 9dB worse than others after manufacture, you may have an ESD problem this most likely will also result in a higher field failure rate than would otherwise be the case, get whoever is responsible for ESD protection to check all machines for ESD, environment for correct humidity etc. 

  • 0 in reply to Russel Hughes
    Guru 36490 points

    Hi Russ-san,

    Thank you for your prompt reply.

    Have you experienced characteristic degradation related to ESD ?
    I would suspect popcorn noise as the root cause.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    Prodigy 170 points
    I have seen ESD cause problems in manufacture and as popcorn noise is related to the amount of defects a device has, I would expect popcorn noise to increase if a device is subject to any form of electrical overstress, I guess the only way you will find out is to test the devices before manufacture to see if the popcorn noise increase but I guess that would be difficult.
  • 0 in reply to Russel Hughes
    Guru 36490 points

    Hi Russ-san,

    Thank you for the information.

    We are asked to investigate this root cause from our customer, but I don't think that useful information can be obtained from devices with degraded characteristics.
    So, could you please tell me how to measure the characteristic degradation related to ESD without measuring noise characteristics ?

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    Prodigy 170 points
    If you suspect a noisy part is caused by ESD damage, may be Ti could analyse the part for you.
  • 0 in reply to Russel Hughes
    Guru 36490 points

    Hi Russ-san,

    Thank you for your quick response.

    If the LME49860 potentially has the popcorn noise with the bipolar process, there is no need to investigate the root cause.
    So, we would like to confirm whether the popcorn noise could be detected with ATE.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    Prodigy 170 points
    Hi,

    It wasnt clear whether the problem with popcorn noise is an intrinsic problem with the LM49860 or something that was induced in the assembly process, If it is intrinsic to the device and it is to spec, I guess the best way to look for it is with an instrumentation amplifier with a low pass filter and then set a threshold.
  • 0
    TI__Guru* 95145 points
    Hi Kato-san,
    Based on previous discussion, unfortunately popcorn noise might be an issue for bipolar devices such as LME49860 and LME49720.
    Also from previous discussion it seems that devices might need to be screened on the actual application, perhaps Russ comments could help you as well.

    Hi Russ,
    Thanks for your comments.

    PD. Previous discussion on popcorn noise: e2e.ti.com/.../1498993

    Best regards,
    -Ivan Salazar
    Applications Engineer - Low Power Audio & Actuators
  • 0 in reply to Ivan Salazar
    Guru 36490 points

    Hi Russ-san and Ivan-san,

    Thank you for the comment.

    We will try to confirm whether the root cause is the popcorn noise by measuring an inverter amplifier with gain of 40dB.
    So, we will discuss this issue with our customer and suggest him to screen the devices on the actual application by himself but he will not be convinced.

    Best regards,
    Kato

  • 0 in reply to Sadanori Kato
    Guru 36490 points

    Hi Ivan-san,

    I am facing the following symptom, so is it possibility to occur this symptom if LME49860 might be damaged by EOS ?
    This is the result of 101 times the noise gain.
    It seems that this symptom might be the popcorn noise.

    Could you please give me your advice about this issue ?

    Best regards,
    Kato