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TXB0102: 3.3V out can not reach 3.3V.

daniel
Genius 5095 points
Part Number: TXB0102
Other Parts Discussed in Thread: TXS0102, TXS0101, SN74AXC1T45

Hi Team,

We use TXB0102 for level shift 1.8V to 3.3V bi-direction.

But we can not get 3.3V on B1 pin, only get about 1.8V. schematic as below.

1. Could you help to explain why? Is the driving current no enough?

2. We may change to TXS0102 for better driving capability. Use the same schematic, only change IC. Is the structure OK?

3. Customer wonder TXS can support push pull and open drain signal, why still has TXB series which can only support push pull signal?

     Any advantage for TXB on push pull application?

Thanks

  • 0
    TI__Guru 56010 points
    Hi Daniel,

    These are 2 different applications, one with open drain( OD) and another with push pull signal trying to drive LED IC.
    The TXB is a weak driver and not suited for OD applications. There is an internal 4K resistor and the external 4.7K resistor forms a voltage divider at B1.
    B2 has 0.1uF/ 100K pulldown, the 100K pulldown might be fine, but not the 0.1uF. TXB devices cannot drive that load cap or the LEDs.
    I would suggest to use the TXS0101 for interfacing the OD signal, and remove the 4.7K pullup since the TXS has 10k internal resistor.
    For the LED driver signal, consider using the SN74AXC1T45 which is active buffer suited for 12mA drive strength at the output. It may still struggle to drive the 0.1uF, consider removing cap if not required.
    Let me know what you go with.