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SN74CBT3245C: VGS value of the SN74CBT3245C

HUI XIE
Prodigy 30 points
Part Number: SN74CBT3245C
Other Parts Discussed in Thread: LSF0108, TXU0104, SN74LXC8T245

What is the VGS value of the SN74CBT3245C series parts?

When the device is used for 5V to 3.3V conversion, do I need to refer to the following circuits for the design?【When connecting an external diode between the 5V power supply and the VCC pin of the device, what is the forward voltage(VF） of the diode?】

  • 0
    Guru 266610 points

    This is an old device designed for digital TTL signals; as shown by the ron specifications, only signal voltages up to 2.4 V are deemed important.

    A normal silicon diode's forward voltage is about 0.7 V. The pass transistor's gate-to-source threshold and behaviour are not directly specified, so it would not make sense to specify VGS.

    What is the actual problem you're trying to solve? For level conversion, better use the LSF0108, or a buffered translator like the TXU0104 or SN74LXC8T245.

  • 0 in reply to Clemens Ladisch
    TI__Genius 13640 points

    Hello I agree with Clemens

    Please let us know what you think about his suggestions!

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 30 points

    I want to use  SN74CBT3245C for  PCI-X data bus switch, but we used to have an IC of PI5C3245, and I want to use SN74CBT3245C to replace PI5C3245,Is it OK to replace PI5C3245 with SN74CBT3245C?When using the PI5C3245 chip, a diode and a resistor are used around the Vcc pin (below), if the SN74CBT3245C chip is used, do I need to use a diode and a resistor as well, and if so, are there any special requirements for the VF and resistance values of the diode?

    Thanks

  • +1 in reply to HUI XIE
    Guru 266610 points

    Do you need a P2P replacement? In that case, use a CBT3245 switch, but check the result, because you are relying on unspecified analog characteristics.

    The LSF0108 would make a better job of clamping voltages to 3.3 V.

  • 0 in reply to Clemens Ladisch
    TI__Genius 13640 points

    Hello Just to add on to what Clemens said,

    The CBT3245 is a  good replacement for the PI5C3245( Like Clemens said).

    The use case you are trying to have with the CBT3245 should be fine and is talked about in this app note.

    Regards,

    Kameron