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Original question:

TXB0104: Review & comment my schematics.

TXB0104: status changes issue in FCT test

user5411045
Intellectual 270 points
Part Number: TXB0104
Other Parts Discussed in Thread: SN74LVC8T245,

Problems when FCT test：
When ES+/- or Encoder _+/- changes from +5V->0V or 0V->5V ，RO or EQEP usually can't achieve +3.3V->0，somtimes remain +1.7v-2v。

  • 0
    TI__Guru 61970 points
    Hi,

    do you have the scopeshots on the input and output channels?
    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?
  • 0 in reply to ShreyasRao
    Intellectual 270 points

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    ShreyasRao said:
    Hi,

    do you have the scopeshots on the input and output channels?

    No，is there any test spec ?

    I see that there are pullup and pulldown resistors on the 5V side, what is the loading on the 3.3V side?

    Direct to Mcu，no other things.

  • 0 in reply to ShreyasRao
    Intellectual 270 points
    Not test as your requirement,is there any test spec?+3.3v signals direct to mcu，nothing else.
  • 0 in reply to user5411045
    TI__Guru 61970 points
    What is the FCT testing spec?
  • 0 in reply to ShreyasRao
    Intellectual 270 points
    Function Test in manufacture to verify the ic function.
  • 0 in reply to user5411045
    TI__Guru 61970 points
    Got it, so its the normal operation verification which is failing.
    I dont see the scopeshots. Do you know the ratings on the scope probes? 1Mohm, passive 10x probe? sometimes, configuring it as 50ohm and using 1X probe adds high loading which the device wont be able to drive or handle.
    If not, is there additional loading on the PCB which is not shown on the schematic?
  • 0 in reply to ShreyasRao
    Intellectual 270 points
    We pull high by 10kohm resistor for TP11，then Tp10 can't achieve low. Tp10(3.3v signal side) direct to Mcu，Tp11(5v side ) direct to connector，nothing else.
  • 0 in reply to user5411045
    TI__Guru 61970 points
    I would recommend using the SN74LVC8T245 device which has stronger drive current strength (32ma) as compared to the TXB0104 (20uA).
    It can drive low and drive high effectively better than TXB0104.