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SN74ALVC164245 .. during power-up ...

Rick Bogdan
Intellectual 930 points
Other Parts Discussed in Thread: SN74ALVC164245

Customer has design with SN74ALVC164245 .. during power-up VCCB (5V) tracks VCCA (3.3)  until 1.7V .. then stays at 1.7V for  ~40mS later before going to 5V .. is monotonicity required during power-up on VCCB?  Below is scope capture of VCCA (3.3V) and VCCB (5V)  .. per the data sheet and app note this appears ok but no mention of monotonic ramps are mentioned.  see attachment for scope shot .... 7610.screen_shot1.docx

 

 

 

  • 0
    TI__Genius 14317 points

    Hi Rick,

    I don't think that the 40 ms "event" on the Vccb power-up ramp is of any concern. However, what is of concern is the fact that Vcca should come up completely before Vccb begins to come up. See the attached App. Note page 7. Given the power sequencing in the scope shot, you might want to consider using the LVC16T245 since it doesn't require power sequencing.

    scea021a.pdf