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TXS0108E: The TXS0108ERGYR device don't work normally.

Went Cao
Genius 5550 points
Part Number: TXS0108E
Other Parts Discussed in Thread: TXB0108, TXB0106, SN74AXC8T245

Hi,all

      Sometimes, my TXS0108ERGYR device don't work normally sometimes, when power on. The phenomenon is as follows:

      When the inputs of A1~A8 are changed by high or low,but the outputs of B1~B8 wouldn't be aways high, and the OE pin would be drop down to 0.2V (normal 1.8V). Then I let power down  30 minutes at least, the device can work normally.

      

  • 0
    TI__Guru 58600 points
    Hi Went,

    Trying to understand the question here. When the inputs A1 -A8 are changed from low to high or high to low, the outputs are always high or always low?
    OE is connected to Vcca, but it drops to 0.2V even with Vcca tied to 1.8V?
    Please attach the schematics of the TXS.
  • 0 in reply to ShreyasRao
    Genius 5550 points

    Hi,Shreyas

       Yes,you are right.

  • 0 in reply to Went Cao
    TI__Guru 58600 points
    Hi Went,

    I see that you are interfacing SPI and UART signals using the TXS.
    We strongly recommend using TXB0108 or consider TXB0106 since you have 2 unused IO pins in the schematic.
    TXB is buffered device family which are suited for push pull signal interface like the SPI and UART.
    Alternate option is to consider using our newly released SN74AXC8T245 device which has 2 DIR control pins especially for SPI and UART interface applications.

    Let me know if this is possible.
  • 0 in reply to ShreyasRao
    Genius 5550 points
    Hi Shreyas
    Thanks your recommend,I will recommend customer to use TXB device.
    But now, could you please tell me what is wrong with the question? Thanks a lot.
  • 0 in reply to Went Cao
    TI__Guru 58600 points
    Went

    I do not see anything which could cause issues. Is R324 connected on the OE pin and what is the value?
    10k on the OE line is ok.

    are there scopeshots showing the issues? what is the driving capability of the host?
  • 0 in reply to ShreyasRao
    Genius 5550 points

    Dear  ShreyasRao

         There is not a resistance on the R324,it is just reserved.

           I use multimeter to test the voltage of  B1-B8,so there is not scopeshots showing.

            The host is Qualcomm device,can driving 20mA.

  • 0 in reply to Went Cao
    TI__Guru 58600 points

    Went,

    I am not sure if using a multimeter is a good idea to measure signals which are switching.

    Measuring DC signals will be ok. I am concerned with the OE pin going to 0.2V. Is it happening with single device or with all the devices?

  • 0 in reply to ShreyasRao
    Genius 5550 points
    Dear Shreyas
    I'm sorry for later.
    1. Because it is probabilistic on some devices , so I think it's happening with all the devices.Now,there are new devices happening.
    2. I have a new question, please help me:
    When the device happens with this problem, how can I recover the device to work normal as soon as possible. Because I must make the device to power down(VCCA\VCCB\OE off) about 0.5 hour, it's so long time.
    Thanks a lot.
  • 0 in reply to Went Cao
    TI__Guru 58600 points
    Went,

    you have a 1uF cap on the supplies and most likely the half hour is consumed for discharging the cap.
    usually, a 0.1uF cap should be sufficient as a bypass cap. This should discharge faster allowing to reset the device sooner.
  • 0 in reply to ShreyasRao
    Genius 5550 points

    Hi ShreyasRao

         I will try it, use 0.1uF cap on the supplies.

         And, the 33Ω resistance on the supplies is suited ?

  • 0 in reply to Went Cao
    TI__Guru 58600 points
    hi Went,

    A series resistor on the supply pin is unusual. As the power consumption increases, the series resistor will have larger drop across it reducing the voltage at the device pin node.
    It may be beneficial, while in small current loading application, in terms of reducing the overshoot of the IO channel, by the reducing the voltage droop.