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CD4051B: difference of Switching Waveform between two units

Shinichi Inoue
Guru 20926 points
Part Number: CD4051B

Dear Specialists,

My customer is evaluating CD4051B and has a question.

I was wondering if you could advise.

---

I am confirming two CD4051Bs, falling waveform is quite different.

One device naturally falls in voltage.

In other devices, the slew rate changes while the signal falls.

I'd like to confirm whether this device is normal.

I'd like to know if this is broken.

Please see attached file

---

I appreciate your great help in advance.

Best regards,

Shinichi

question about CD4051B.pptx

  • 0
    TI__Intellectual 2900 points
    Hi Shinichi,

    The first scope shot shows abnormal behavior and the signal falling edge profile is not what I expect.

    Would you swap the CD4051B between two boards and capture the waveform again? I would like to compare if there is a board difference.
  • 0 in reply to Fan.Wang
    Guru 20926 points

    Hi Fan,

    Thank you for your reply.

    In this case, the device was tested another board and observed the same waveform.

    I think the device is something wrong.

    Do you think should I request a failure analysis.

    I appreciate your great help.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    TI__Intellectual 2900 points

    Hi Shinichi, 

    If another CD4051B unit works for your customer, I don't think we need to look into the failure root cause of this particular unit.

    CD4051B's yearly shipment is pretty significant and it has been in the market for so many years. The likelihood of device malfunction is very low. Please feel free to let me know if you have a different opinion. 

  • 0 in reply to Fan.Wang
    Guru 20926 points

    Hi Fan,

    Thank you for your reply.

    I'm sorry for late reply.

    I told the customer it may be not malfunciton and investigate more precisely.

    if he has an additional question, I consult you again.

    I appreciate your great help.

    Best regards,

    Shinichi

  • 0 in reply to Shinichi Inoue
    Guru 20926 points
    Hi Fan,

    Long time no see.

    I talked with the customer, he understand the device is not failuar.

    But he need to improve falling waveform.
    Because he would like to adopt the device as standard.

    I was wondering if you could advise.
    ---
    (1) Is there a possibility of improve by adding external component, for example comparator or buffer ?

    (2)Is there another device with good falling characteristics?
    ---
    I appreciate your great help.
    Best regards,
    Shinichi
  • 0 in reply to Shinichi Inoue
    TI__Intellectual 2900 points

    Hello Shinichi-san, 

    Absolutely I can help in this case. By improving on the falling edge characteristics, what specifics would you like to improve on? Are you looking for a faster falling edge? 

    Also, would you send me your schematic with the CD4051B surrounding circuitry? I can look into whether adding external devices or using a different device will make more sense. 

  • 0 in reply to Fan.Wang
    TI__Mastermind 45495 points
    Shinichi,

    We haven't heard from you in a couple of weeks. Has Fan resolved your issue?

    Thank you,
    Adam
  • 0 in reply to Adam Torma
    Guru 20926 points

    Hi Adam and Fan,

    Thank you for your reply.

    And I'm sorry for late reply.

    My sales talked with the customer.

    ---

    (1) The customer wants to improve the device side.

    They wanted to adopt for new model, but the fall time is unacceptable. 

    (2) They don't want to add external circuit.

    Because it is necessary to change the existing circuit.

    ---

    I think that it is impossible to improve the device even though there is a problem in the falling edge at the customer.

    Because this device is not defective, it is on the market in large quantities.

    Based on these circumstances, there is nothing we can do right now.

    So we would like to see the situation.

    Your follow-up made it clear.

    I appreciate your great help and cooperation.

    Best regards,

    Shinichi