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TXS0104E: Hot swap issue in TXS0104

Part Number: TXS0104E

Hi team,

My customer use the TXS0104 in the PCIE card in the server.

The PCIE card will plugged in the server mother board.

Below is the schematic of the TXS0104 in the PCIE card.

     The schematic in PCIE card

The port B is connect in the mother board. In the mother board, they use the 4.7k resistor to pull up to 3.3V.

The operation sequence is as below:

1. The signal direction is from port B to port A. The PCIE board is powered by the mother board.

2. In the mother board, the 3.3V voltage and the PCIE_PEWAKE_N is high firstly.

3. When the PCIE board plugged into the mother board, the mother board will supply the TXS0104.

4. So during the period when PCIE board plugged into the mother board, the PCIE_PEWAKE_N signal will be affect and show the low pulse(as below).

5. Note, during the pulse occur, they has monitored the VCCA, VCCB and OE pin in our part, the voltage of three pin are all low.

So the issue happened when the PCIE board plugged into the mother board and before PCIE board power up the part.

Please help to analyze the application above, and reply below question:

1. What may be the cause for the issue? Does this situation make sense?

2. Is there any solution to avoid the effect for the input signal of the port B?

3. Is the pin in the part high impedance before we power up the part?

Please help to reply as soon as possible!

Lacey

Thanks a lot!

  • Hi Lacey,

    The TXS device is not designed for the live insertion or guarantee performance for hot insertion.
    The A/B IO ports are hiz and unknown level before the power supply is up.
    Having a weak pull up > 50k on the B port may help avoid the situation ( although I do not usually recommend having a pullup on the IO ports).
    2.2K pullup on the A ports can be removed or replaced with a weaker pull-up, if possible.