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SN74ALVC164245: SN74ALVC164245DGG issue

user3434218
Intellectual 690 points
Part Number: SN74ALVC164245
Other Parts Discussed in Thread: SN74AXC8T245, SN74LVC8T245

Hi，

When VCCB start，What are port-B's status until VCCA start?

How can we keep port-B's output low level until VCCA start?

In our function,VCCB will start before VCCA，Port-B's status is very important at this time。

  • 0
    Guru 316860 points

    As far as I can see, section 10 of the datasheet does not allow you to power up VCCB before VCCA without getting problems.

  • 0
    TI__Guru 62130 points

    What is the application's operating voltage levels? This device doesnt have Vcc isolation / Ioff protection. May be for 2.5V<> 3.3V with SN74AXC8T245. 

    For 3.3 <> 5V case, you can consider using the SN74LVC8T245 which provides Vcc isolation ensuring that the IOs are in HiZ when either of Vcc is low.

    I recommend having a weak pulldown to ensure that the low level is ensured on IOs.