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Expansion board level shifter -  TXS0180E - how do we put it in push-pull mode?

romilly

Some of you may know that my company (Quick2Wire)  is working on a number of add-on boards for the Raspberry Pi.

 

We've hit an issue with the main interface board, and I'm hoping one of the engineers here can help.

 

We'd like to use a TXS0180E to level-shift the eight GPIO pins of an ARM SoC. We need stronger outputs than the TXB0108PWR..TXB0108PWR.. provides. The data rate of the TSX0108E is fine in push-pull mode but would be too slow in Open-collector mode.

I'm confused, though, about what determines the mode in which the chip operates. How do we control whether it's in Open-collector or push-pull mode? Is it just a matter of whether we have pull-ups attached to the lines?

 

It's not a show-stopper, as we know that we can use a TXB0108PWR..TXB0108PWR.. with a ULN2803, but that adds to the cost. I'd like to avoid that option if we can.

 

Thanks,  Romilly

Parents

  • Would the SN74LVC4245APW...SN74LVC4245APW... not do what you want?

     

    There is another chip, MC74AC244 which has a Vcc spread of 2v0 -> 6v0  with Vin/Out equal to 0v -> Vcc, current drive of 24mA per pin. I was thinking of making an interface board with one of these myself and then decided I might buy your one instead.

     

    The TI site search doesn't come up with your part number, so I can't compare that part withy the ones I mentioned.

     

     

    Colin

     

    PS: Found it - I wish TI would sort out their search engine.

    PPS: I see why you are thinking of this chip, I assume the auto direction facility is the attraction.

  • in reply to bodgy

    Looking at PDF scea044 (A guide to Voltage Translation with TXS-Type translators), it seems that if no external pull up resistor is used then the output is push-pull, with an external pull up it acts as though it were an open-collector.

     

    Colin

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