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SN74LV4T125: Drive current needed on xA input pins to shift

Brian Antheunisse
Expert 5305 points
Part Number: SN74LV4T125
Other Parts Discussed in Thread: TXB0104

Hi team,

I have a customer thinking about using the SN74LV4T125, but they have had problems in the past with their input signal not being strong enough to drive input pins enough to make the change.

What is the input current requirement for VI = 0 and VI = 5V when VCC is set to 3.3V? This is to down translate from 5V to 3.3V.

I know that some of the TI buffers have a bus-keeper circuit where the input has to be driven hard enough to switch state from 0 to VCC or VCC to 0. I was wondering if there is such a requirement for this device. My customer rain into this when they used the TXB0104.

Thanks!

Brian

  • 0
    Guru 317750 points

    The TXB is not a 'normal' logic device; the auto-direction-sensing circuit indeed behaves similarly to a bus-hold circuit.

    The SN74LV4T125 uses plan CMOS inputs, which are just the gates of two MOSFETs. The current requirement is approximately zero (see CI and II in the datasheet).