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SNJ54AC244W input characteristics

Jamaal_Charles
Genius 3245 points
Other Parts Discussed in Thread: SN54LVCH244A, SN54LVC541A, SN54LVTH244A

Hello,

We have read through the SNJ54AC244W datasheet and this document on CMOS devices http://www.ti.com/lit/an/scba004c/scba004c.pdf, but I'm having trouble finding the following information...

If we are using this part as a receiver on a bus, what are the input characteristics when:

  1. The part is powered off
  2. At time of power up and down
  3. The outputs are tri-stated (OEn is high)

We are trying to avoid corruption of the data on the active bus when our module (and this part) are powered down.

Thanks for your help

  • TI__Guru 62930 points

    When powered down, the outputs will load the bus, as they will not be logically functioning.

    The specification for output voltage range is -0.5v to VCC +0.5v.  So, if the device VCC = 0, then the output buss that it is tied to cannot exceed 0.5v.  An ESD diode to VCC with begin to conduct current.

    The feature that you desire is called Ioff and power-up tri-state (PU3S).  This will minimize current flow when device is powered off and keep device in tristate during power sequence.

    There are several octal mil temp range devices that may meet your needs.

    The SN54LVC541A, SN54LVCH244A, SN54LVTH244A all have Ioff. 

    Regards,

    Wade

  • in reply to Wade Vonbergen
    Genius 3245 points

    Thanks Wade,

    Just to clarify,the INPUTS will not load the active bus that we are a receiver on while we are powered off, and when we switch power on/off?

    Thanks again

  • in reply to Jamaal_Charles
    TI__Guru 62930 points

    Eric,

    The input range is the same as output range in the abs max section.  -0.5v to VCC+0.5v.   With VCC =0, it will load the bus, if the bus tries to drive above gnd.

    Regards,

    Wade