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TXS0108E: component issue

GARETH OU
Guru 10295 points
Part Number: TXS0108E
Other Parts Discussed in Thread: SN74AXC8T245

Hi 

Problem description:

1. When the LTEVCC_EN signal in the circuit diagram turns on the 3904 transistor of Q68, the LTEVCC_EN signal will jump up and down due to insufficient drive capability
2. TXS0108ERGYR is a two-way Level shift IC, which causes the LTEVCC_EN_SOC of the input signal to be affected and jump up and down.
3. Then the PMU_PLTRST_N of different channels is also affected and cannot be pulled high normally, causing the board to fail to boot normally, and the OE signal is not affected
4. Q68 must be changed to 2N7002 transistor before it can return to normal

Questions:
I refer to the content of the datasheet, TXS0108ERGYR is an IC that is opened independently for each channel. Why does it affect the signals of different channels?

  • 0
    TI__Mastermind 44775 points

    Hey Gareth,

    I'm not exactly sure I follow the question completely here, but its likely each channel is having issues since this is not a suitable application for the TXS device. This device provides no drive strength of its own, it relies on the drive of the interfacing devices and 4kohm pull-ups. Connecting it to  BJT is likely going to cause issues like the one you are seeing. I don't think one channel is affecting others, its more likely due heavy loading on those other I/O or external pull-ups/pull-downs.

    If these are unidirectional signals or signals with fixed directions, I recommend using device like the SN74AXC8T245.