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SN74AXC8T245: Requesting part recommendation for I²S Mux, I²S Level Translator, I²C Level Translator

UA&A_CodyDowling
Expert 1006 points
Part Number: SN74AXC8T245
Other Parts Discussed in Thread: SN74LVC157A, 2N7001T, SN74AXC1T45, TXS0102, TCA9800, TMUX1574, TXS0108E, TXB0104

TI Team,

We are currently working on a wireless headset design and have a need for some muxes and level translators. We have used the SN74AXC8T245 in previous designs but are looking for a smaller, more integrated and easy to use solution. Out block diagram looks like this:

For the 3 parts shown, could you please recommend the smallest/most integrated solution we should consider from TI? (I'm not sure if it is possible but, if we could find an I²S Mux that also did level shifting it would be really great.)

Thanks so much for your help!

Cody

  • 0
    Guru 316960 points

    What is the clock frequency?

    As far as I can see, the SDOUT signal does not need muxing.

    LVC devices have overvoltage-tolerant inputs, so you can simply run a multiplexer like the SN74LVC157A at 1.8 V. To translate SDOUT, use the 2N7001T or SN74AXC1T45.

    For I²C, use the TXS0102 (requires no external pullups, but does not handle noise or high capacitances (are there long traces?)) or TCA9800 (requires only one set of pullups).

    Alternatively, a single translator for all seven signals would result in the TXS0108E (because of the I²C open-drain signals), plus a separate mux like the TMUX1574.

  • 0
    Expert 1006 points

    Hi Clemens, 

    Thanks for your quick and helpful answer! Relaxed

    Re: Clock Frequency- Fastest is MCLK at 24.576MHz, slowest is 48kHz, I²C would only run up to 400kHz

    Re: Component selection- To maximize re-use and gate integration, could I use 3 of the TS0104E devices (as shown in diagram below)? If I can use the output enable (OE) to put the outputs in High-Z, I think I can connect their outputs together- correct?

    *EDIT* just noticed that the SDOUT arrow was pointing the wrong way on the bottom most translator. I think you get what I mean though... Sweat smile

  • 0 in reply to UA&A_CodyDowling
    Guru 316960 points

    The maximum speed of the TXS is 24 Mbps = 12 MHz. (I guess this is enough for SDOUT.)

    The TXB0104 can support 60 Mbps, but has very strict load requirements. Two of them would work in this scheme, but when you already have a separate TXS, a single 74xx157 might be preferrable.