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TXU0204: Can VCCB be powered off while VCCA is on?

js
Prodigy 120 points
Part Number: TXU0204
Other Parts Discussed in Thread: TXB0104,

Tool/software:

I need a level shifter for GPIO lines where one side (VCCB = 5V) can be powered off while the other side (VCCA = 3.3V) is on. 

The TXB0104 level shifter claims to have the Vcc isolation feature (if either VCC input is at GND, all outputs are in the high-impedance state). But it also says, VCCA must be ≤ VCCB. Therefore, it doesn't seem suitable.

TXU0204 also claims to have this Vcc isolation feature, but it doesn't mention the VCCA ≤ VCCB condition, but also doesn't say clearly if VCCB can be powered off while VCCA is on.

Could you please confirm if TXU0204 can be used in such condition?

Thank you!

  • +1
    TI__Mastermind 25620 points

    Hello JS,

    As you noted, the TXB0104 has the VCC isolation feature but only when VCCA or VCCB equals GND. If either supply is left floating, the I/Os will not enter a high impedance state

    The TXU0204 supports both VCC isolation and VCC disconnect. This means if either supply is GND or left floating, I/Os will enter a high impedance state. The TXU204 does not have the supply restrictions as the TXB0104. 

    To answer your question, yes the TXU0204 can have VCCB powered off while VCCA is on. Hope this helps.

    Regards,

    Josh