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SN74CBTLV3257: Level shift function

Shu-Cheng LIN
Guru 11785 points

Part Number: SN74CBTLV3257
Other Parts Discussed in Thread: TMUX1511

Hi Sirs,

Sorry to bother you.

We plan to use this MUX on JTAG singal between CPU(1.0V) and BMC(3.3V).

Our Vcc is 3.3V.

In our understanding, the rail-to-rail switching is means this IC can support +-VDD level shift.

But we not sure is this MUX supported level shift or not? or I need add a GTL IC(SN74GTL2014PWR)?

If yes, there are TDI and TDO in the JTAG signal, so I need two SN74GTL2014PWR(one LVTTL, one GTL)?

Thanks!!

Thanks!!

  • 0
    TI__Mastermind 45780 points

    Shu-Cheng,

    The SN74CBTLV3257 is widely used in JTAG switching between CPUs and BMC.   This device has rail to rail switching which means it will not attenuate signals that pass through the switch over the entire voltage range 0 to Vcc.  This doesn't have any level shifting capability but will pass any signal up to Vcc.  

    We are also seeing the new TMUX1511 device start to get picked up for JTAG applications as well.

    To achieve level shifting function you will need to use a level shifting IC.  

    Thank you,

    Adam