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TXB0106 chip auto-direction applied per bit or per port?

Macpod
Prodigy 10 points
Other Parts Discussed in Thread: TXB0106, MSP430F1611, SN74AVC4T774

For the TXB0106 chip, does the auto-direction sensing apply per bit or to all 6 bits at once?

I.e. Could I transmit signals as follows SIMULTANEOUSLY?:
A1->B1
B2->A2

A3->B3
B4->A4

A5->B5
B6->A6

I'm interpreting page 9 of the data sheet as suggesting it works per bit but I wanted to verify.

 

 

  • 0
    TI__Genius 9085 points

    Yes, the TXB chip autp-direction senses per bit.

    You can simultaneously transmit in different directions on different ports.

     

    A1->B1
    B2->A2

    A3->B3
    B4->A4

    A5->B5
    B6->A6

    The above will operate correctly.

     

     

  • 0 in reply to Hattie
    Prodigy 30 points

    Hello,

    Good to see this thread, as I had the same question. I notice that the input impedance (resistance) is not listed on the datasheet. I've placed the TXB0106 between the MSP430F1611 (running @ 2.9V) and an ASIC running at 1.2V. The TXB0106 connects the 32kHz clk signal from MSP430 port 2,0 to the ASIC as well as SPI CLK and SPI data from the ASIC to the MSP430 ports 5,3 and 5,1. I can see that the TXB0106 seems to load the Data SPI and CLK SPI signals despite the ASIC's output being buffered.

    So since you say that the input pins of the TXB0106 can run in different directions on different ports, it looks like the input pin of the TXB0106 is loading the SPI CLK and SPI data ports of the ASIC. I can see in the datasheet pg 8 that the input capacitance is between 35-26pf, but i cannot find a value for the input resistance. I can go and measure the resistance, but I'd like to know if anybody else has done this already.

    Hence my question: does anybody have a value for the input resistance of a TXB0106 port?

    Thanks in advance.

  • 0 in reply to Dilpreet Buxi
    TI__Genius 9085 points

    The buffer resistance is about 4kOhm, so your system needs to be capable of driving 4kOhms. Below is a link to an application note on using the TXB translators.

    http://focus.ti.com/lit/an/scea043/scea043.pdf

     

    For SPI another choice might be the SN74AVC4T774, since the signals are single direction.

  • 0 in reply to Hattie
    Prodigy 30 points

    Thanks Hattie. Will try the replacement part. Best,

    Dilpreet