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TXS0104E: Output spur in low temperature

Lacey Lin
Intellectual 2900 points
Part Number: TXS0104E

Hi team,

my customer use the TXS0104 to translate the voltage of SMBUS. below is the schematic:

And they find in the -40°C, there will show the spur in CLK occasionally.

1:SMBUS DATA

2:SMBUS CLK

3:3.3V supply

It seems when the spur show, there is also a vibration in 3.3V supply.

So can you give your comment if the vibration in 3.3V can cause this?

Or what may be the root cause?

Lacey

Thanks a lot!

  • 0
    TI__Guru* 97046 points
    Hi Lacey,
    Thanks for the detailed post. I will ask our translation expert to take a look on Monday.
  • 0
    TI__Guru 62280 points

    Lacey,

    When you mention that the issue is seen at -40c, does that mean that other temp operations don't have this issue or if the application is only being run at -40C?

    is the Vcc ringing seen at other temperatures as well or only pronounced at -40C? I do notice from the schematic that there are no bypass caps on the Vcc supplies, correct me if there is.

    Also, there are strong pull-up resistors on the IO ports which are not advised, please read the app note about external pullup on TXS devices.

    There are internal pull-up resistors in the TXS devices which is there to avoid having external resistors. There is also significant cap loading on the lines which are not advised either but it actually helps in suppressing the glitches seen. how long is the trace? The layout section suggests having short traces to avoid the reflection to create false triggering through the one-shot circuitry.

    I would advise having bypass caps close to the device supply pins and remove external pull-up resistors and the additional cap on the lines.

    Let me know if this helps.

  • 0 in reply to ShreyasRao
    TI__Intellectual 2900 points

    Hi Shreyas,
    Thanks very much for your reply!
    you recommend to remove the 4.7K pull up resistor and 100pF cap in the output and also the resistor and cap in the input. is if correct?
    I will also double check situation of the supply vibration and supply cap with customer. and will update the information.

    From the information customer gave before, the issue only exist in low temperature.

    Do you think what may be the root cause？ The supply or the pull up resistor?
     
    Lacey
    Thanks a lot!

  • 0 in reply to Lacey Lin
    TI__Guru 62280 points
    Hi Lacey,

    The device have been tested to guarantee that it works at all the temp range mentioned in the datasheet.
    so, not working at low temperature (which should be within Ta of the datasheet) is a cause of concern on reliability and is not expected to behave as such.
    The other recommendations on bypass caps and pullup resistors are guidelines for TXB device. This may or may not be the root cause of the issue the customer is facing.