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SN74ABT126: Enquiries

Nazirul Harun
Prodigy 70 points
Part Number: SN74ABT126

Hi,

Based on data sheet, absolute maximum rating specification is -0.5V to 7V.

Then, on  recommended operating conditions state that it should be on 4.5-5.5v.

My question is, if we are using VCC input for 3.3V;

1- Is it the IC still going to function?

2-Is there are any impact/application?

*the board is not tested under extended periods but instead just an ICT (In-Circuit Test) tester

Thanks.

Regards;

Nazirul

  • 0
    TI__Guru* 96591 points
    Hello Nazirul,
    We offer many devices that have the 126 function and are designed to operate at 3.3V -- is there a reason you aren't using one of those?

    Absolute Maximum Ratings is basically telling you the range of voltages that the device can safely tolerate -- it won't necessarily operate over all of that range, but it won't be broken by applying a voltage anywhere in there.

    The Recommended Operating Conditions table gives the values that we tested for on the datasheet. If you operate the device outside of that range, it will likely function, however we will not guarantee any of the specs int he datasheet (current, voltage output, timing, etc.)
  • 0 in reply to Emrys Maier
    Prodigy 70 points

    Hi Emrys Maier,

    We are using this model for over than two years, the model and VCC input voltage are follow our customer specification.

    Past this two years, there are no problems occur but for last date code we received which is 72 & 74 we are having a lot of failure.

    Problems statment;

    -Output pins 3, 6, 8, and 11 measured high level output (around 1.7V). This output pins supposed to be in low level (ideally 0V).

    Based on logic table, the IC need to satisfy the condition to be able to turn on the LED’s connected to the output pins 3, 6, 8 and 11.

    But using the fail IC, we are seeing  high logic output and that’s why it fails in the ICT test.

    Swap test also done to verify with other older date code and the result show the failure follow the defective/suspected date code which is 72 & 74.

    If our VCC input voltage is the root cause of this problem, definitely we will have this issue a long time ago. 

    Thanks.

    Regards, Nazirul.

  • 0 in reply to Nazirul Harun
    TI__Guru* 96591 points

    Have you contacted your local TI Sales office to start a failure analysis (FA)?

  • 0 in reply to Emrys Maier
    Prodigy 70 points
    Already sent for FA. and the result is pass ATE testing and no anomaly on curve tracer.
  • 0 in reply to Nazirul Harun
    TI__Guru* 96591 points
    I'm afraid that's as much as we can do. As I mentioned at the beginning, we can't guarantee operation outside of the datasheet recommended specs.
  • 0 in reply to Emrys Maier
    Prodigy 70 points

    Yes agreed with you that we are not follow your recommendation spec. but, by right, the IC still can work as normal as it still in operating specification.

    Furthermore, if we are not follow your recommendation spec is the root cause, why we only see this issue for the last lot we received which is this particular 72 and 74 date code? 

  • 0 in reply to Nazirul Harun
    TI__Mastermind 24485 points
    Hello Naizul,

    If the device passes the ATE, then by our standards the device is a good device and there is nothing further we can do.

    As Emrys mentioned, we only guarantee device operation and electrical characteristics within the recommended operating conditions. While the device sometimes may work at other voltages outside of this range, we do not check those conditions. Variations in process may have changes that effect operation outside of our recommended operating conditions, but do not affect the device within the operating conditions.

    This is the inherent risk with designing outside of recommended operating conditions. If you do, it may work for some time, but it may not always work as we don't test it or guarantee it, so it is not a reliable long term solution.

    If you are operating at 3.3V Vcc, then it would be recommended to use a device such as the SN74LVC126:
    www.ti.com/.../sn74lvc126a

    Best,
    Michael.
  • 0 in reply to Michael J Schultis
    Prodigy 70 points
    Hi Michael,

    You claim that a variations in process may have changes the effect operation.
    Could you advise what is variations in process that has changed?

    Regards,
    Nazirul.
  • 0 in reply to Nazirul Harun
    TI__Guru* 96591 points
    Doping levels, distribution, among many other manufacturing factors can change slightly from one group of devices to another. They are all tested for operation to the datasheet spec prior to shipping.
  • 0 in reply to Emrys Maier
    Prodigy 70 points
    Could you elaborate more on doping levels and distribution?Thanks.
  • 0 in reply to Nazirul Harun
    TI__Mastermind 24485 points
    Hello,

    There is nothing specific we can comment on regarding the doping levels and distribution.
    In short, the key is that process variation (which is inherent in any silicon process) can happen and can affect the operation of a device. This is why all devices are tested to ensure that they meet the specifications that we set forth in our datasheets.

    For operation outside of recommended operation conditions, we don't test anything, so it is possible that if you are operating outside of our recommended operating conditions that the device could change its behavior part to part because we do not guarantee anything about the operation of the device outside of recommended operating conditions.

    We guarantee operation inside of recommended so we test to ensure it will work. We don't provide any guarantee outside of recommended operating conditions, so we do not test our devices outside of these conditions.

    Best,
    Michael
  • 0 in reply to Michael J Schultis
    Prodigy 70 points
    Thanks for the info. Can i said that the changes that has been made started for date code 72 on wards?
  • 0 in reply to Nazirul Harun
    TI__Mastermind 24485 points
    Hello,

    We cannot say that it will behave in any way outside of the recommended operating conditions.
    Unfortunately, we cannot say that it would be specific to devices that fall after a certain date code, as theoretically the device could go back to behaving the way it previously did without our knowledge.

    As long as the device operates to our specifications set forth specifically in the datasheet, we will ship the devices. Any changes to the device outside of these conditions are not tested and therefore we cannot know what changes might exist outside of the recommended operating conditions.

    Best,
    Michael