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TXB0304: B2 Output waveform rising speed gets slow down as the output voltage is closing to VCCB

Part Number: TXB0304

 Hello guys,

 One of our customers is evaluating TXB0304 and they faced the following phenomenon.

1. B2 Output waveform rising speed gets down as the output voltage is closing to VCCB

 (VCCA=1.8V, VCCB=3.3V, B2 Output waveform rising speed gets slow down as the output voltage is closing to VCCB in spit of A2 input is full swing from 0V to 1.8V with 100ns.)

 Have you seen this phenomenon and could you please tell me how to avoid getting slow down rising speed if you know?

 Also could you tell me the following question.

 2. Can we left signal terminal if the signal line is not used?

 Your reply would be appreciated.

 Best regards,

 Kazuya Nakai.

 

  • The datasheet says:

    The TXB‍0304/TXBN‍0304 is designed to drive capacitive loads of up to 100 pF. The output drivers of the TXB‍0304 have low dc drive strength. If pull-up or pull-down resistors are connected externally to the data I/Os, their values must be kept higher than 20 kΩ to ensure that they do not contend with the output drivers of the TXB‍0304.

    What is the capacitive load on the output? (What devices/cables/probes are connected to it?) Any pull-down resistor?

    Unused TXB I/O pins can be left open.

  • Kazuya san,

    Any inputs on this if you were able to fix or work around the issue? As Clemens rightly mentioned , the TXB has weak drive and hence it is designed to not drive more than 100pf reliably.
    I see that the input swing is 0 to 1.8v with 100ns which is exceeding the input rise time requirements by 30ns as well.