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TXS0104 return current issue

user4760726
Intellectual 1195 points
Other Parts Discussed in Thread: TXS0104E, TXB0104

Hi team,

One of our customers is facing the issue regarding to the return current. From the block diagram below, the return current enters from the B1 pin and go to VccB through 10k ohms resistor.As the result, the system gets crash because of the return current. Is there any way to prevent this happen? or do we have any pin to pin IC which can prevent this happened? Please advised. Thanks

Leroy Song

  • 0
    TI__Mastermind 30815 points
    Hello,

    What is the value of the return current that you are seeing? Can you provide us with a schematic of the design?

    Very small leakage currents are possible but there are protection diodes that should prevent any excessive current from flowing back into the Vcc terminals.
  • 0 in reply to aozer
    TI__Intellectual 1195 points

    Hi Aozer,

    The customer doesn't know exactly what the value for the return current is. The schematic of the design is shown below. Basically, the returned current is passing to VCCB (PIN14) from B1 (PIN13). I am wondering that whether the protection diodes you mentioned is integrated in the TXS0104 IC or in the power IC? Also, the customer is wondering that whether or not we have the level shifer that has the protection on the return current (like integrating a diode?). Please let me know and thanks for your support.

    Leroy Song

  • 0 in reply to user4760726
    TI__Mastermind 30815 points

    Hello,

    So, I went to the lab and took some measurements of the leakage on the Vccb pin. As long as the voltage on the the B port pins is withing 100 mV of Vccb, there doesn't appear to be any leakage. As soon as the voltage on the B ports exceeds Vccb by 100mV or more the device begins to exhibit a back current on the Vccb pin. As you can see, I took the measurements for two different TXS0104e devices and obtained very similar results. I think the only way to prevent this kind of back current into the Vcc pins is to ensure that the voltage on the IO ports does not exceed the supply voltage. 

  • 0 in reply to aozer
    TI__Intellectual 1195 points

    Hi Aozer,

    Thanks so much for the experinment and it really helps me a lot. The customer expresses that it is hard for them to the two voltages within 100mV. Do you have any idea or solution to solve the problem? Thanks for your support.

    Leroy Song

  • 0 in reply to user4760726
    TI__Mastermind 30815 points
    Hello,

    Since it looks like you are using a push-pull UART, I would recommend using the TXB0104 instead.