This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

RM46L430: Absolute maximum ratings vs. reliability time

Part Number: RM46L430

Hi, we are using the following design to read a 24V digital signal into the RM46L430 on digital input:

Unfortunately the 3,0V-Z-diode is missed on some PCBs. On these PCBs the input of the RM46 is now driven by 4.0V. Tha means over the maximum recommended signal level but below teh aboslut maximum level. In a footnote is written, that this situation decreases the reliability of the device. Has TI done tests to determine how much the lifetime is shorten as a function of the signal level? And can Ti provide the results to us?

Thank you in advants,

Jens Greiner

  • There is no formula / curve to determine the exact impact on the failure that could be expected as a result of exceeding the max input voltage on a pin. As the datasheet states:

    "(1) Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings
    only, and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating
    conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability."

  • Thanks for the quick answer. But unfortunately this doesn't resolve my problem.

    How did TI tested the values of the absolute maximum ratings? Or in other words, how did TI specified the recommended values? I'm sure that TI has verified the internal protection ciruits of the digital input pins. But how? If there is not no formula or curve, what kind of values exist?

    For example, can you see heating on input circuit more than normal, when the input voltage level of a pin excced the recommended value?

    We don't exccet the absolute maximum value, but we have signal levels up to 4V.  And of course we will add the missing diode where it is possible. But in some cases we can't do this whithout high effort of time. That's why the question.

    Can you provide some values to estimate the loses of reliability?

    Thank you in advance.

  • Hello,

    I check with our quality engineering team and they confirmed that we cannot quantify the effect of violating the specification based on the transistor ageing and stress models.

    Do you also see the entire VCCIO supply go to 4.0V since you are putting in 20mA into the pin?

  • Hello,

    I measured the VCCIO directly. If we have 4.0V on IO-Pin the VCC is still 3,4V.

    Regards,

    Jens

  • We can close this path. We found another solution. Thanks.