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TXS0108E: Questions for Absolute Maximum Rating of Input voltage of TXS0108E.

Kazuya Nakai59
Guru 21705 points
Part Number: TXS0108E


 Hello guys,

 One of my customers is evaluating TXS0108E for their new products.

 They have the following questions about this device datasheet. Could you please give me your reply?

 Q1. In the absolute maximum ratings table of TXS0108E datasheet (Document No.:SCES642F), input voltage, VI is 4.6V for A port and 5.5V for B port as the maxmum value.

        It seems that the values are not changed depend on VCCA and VCCB. In the other words, it is no problem to input higher voltage than VCCA or VCCB.

       But in the recommended operating condition table, VIH maximum voltage is VCCI (=VCC of Input signal side = VCCA or VCCB). This description says that VIH is changed depend on VCCI.

       Which is correct? Is the input maximum voltage changed depend on VCCI? Or not?

 Q2. Is there any parasitic diode between input pin (An, Bn) and VCCI?

 Q3. At figure 12 in the section, 10.2.3 Application Curves, some small overshoot at rising timing of signal are observed. The reccomend condition table says that input voltage maximum voltage is VCCI.

        But can small overshoot (0.1~0.2V higher than VCCi) be allowed because the parasitic diode is not turned on at the small overshoot?

 Your reply would be much appreciated.

 Best regards,

 Kazuya.            

  • 0
    TI__Mastermind 46295 points

    Hi Kazuya,

    It is recommended not go exceed VCCI. The abs max ratings are stress ratings so anything past the recommended can cause reliability issues. If the abs max rating is exceeded , then there can be permanent damage.

    No parasitic diodes to VCC since this device doesn't output buffers but instead a pass FET.

    I believe the signal with more overshoot is the output and that can be caused by the edge-rate accelerator. However, there shouldn't be any concern with overshoots that small.

    Edit: I just realized that you may be asking about ESD clamp diodes when you say parasitic diodes. This device has no ESD clamp diodes to VCC.

  • 0 in reply to Dylan Hubbard
    Guru 21705 points

     Hello Dylan,

     Thank you very much for your reply.

     I understood that this device had no ESD clamp diodes to VCC.

     Could I ask you an additional question?

     Do you have any specific value of overshoot voltage which don't affect reliability and the device function?

     For example, VCCI+0.3V is no problem, etc.

     I know that the device electrical characteristics can not be kept when the device operation conditions is out of recommended operating conditions.

     Thank you again and best regards,

     Kazuya Nakai.

  • 0 in reply to Kazuya Nakai59
    TI__Genius 16735 points

    Hi Kazuya,

    There is no specific overshoot voltage that doesn't affect reliability. It depends on the period of time it is in overshoot. If this happening for a very short period of time, there should be no problem. Although there is no ESD diode to Vcc, there is roughly a 10k pullup going to Vcc. The current from your input would leak into your supplies if you were go above Vcci. This is most likely not going to be okay for your design.

    Thanks!

    -Karan

  • 0 in reply to Karan Kotadia
    Guru 21705 points

     Hello Karan,

     Thank you very much for your reply.

     Your comments are very helpful for the customer and me.

     Thank you again and best regards,

     Kazuya.