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SN74AVC16T245: Vcca Vccb power-up sequence

cafain
Mastermind 6805 points

Part Number: SN74AVC16T245

Hi, staff

I have a question about the level shifter.

Questions concerning the power sequencing in the datasheet of the level-shifter of 1. to 10. below.

There are devices with power sequence comments in the data sheet and devices without comments.
Since they are all the same AVC series, are the power-on sequence all the same?

For a device that does not have a description of the power-up sequence in the data sheet,
is it safe to start Vcca or Vccb first?
(There is no power-up sequence)

The data sheet was compared whether there is description of the power-up sequence or not.
1. SN74AVC16T245DGVR :Not described
2. SN74AVC1T45DBVR :Stated Yes Vcca -> Vccb
3. SN74AVC2T45DCUR :Stated Yes Yes Vcca -> Vccb
4. SN74AVC4T245PWR :Not described
5. SN74AVC8T245PWR :Not described
6. SN74AVCH16T245VR :Not described
7. SN74AVCH4T245PWR :Not described
8. SN74AVCH8T245PWR :Not described
9. SN74LVC1T45DBVR :Not described
10. SN74LVC2T45DCU :Stated Yes Vcca -> Vccb

Is it correct with the understanding that the above-mentioned level shifters are not regulated by Vcca and Vccb in magnitude of voltage?
(It can be used even if Vcca> Vccb, Vcca <Vccb)

best regards

cafain

  • 0
    TI__Guru 63920 points
    Hi Cafain,

    There are no 'requirements' for power sequencing in general. They are only 'recommendations' which may or may not be adhered to depending on the system performance; which means that the power sequencing may be changed according to the requirements of the application.
    Ramping both of the supplies may sometimes not be feasible, so having ports with the side powered up held at ground is advised. My advise is to also have the control inputs and both the IO ports at gnd during the power sequencing through weak pulldowns.
    We have also released a new series of translation devices called the 'AXC', which guarantees no sequencing combinations. Any supplies can be ramped up or down and at varying ramp rates without affecting the IO ports.
    Also, an app note regarding the same can be referred to here:
    www.ti.com/.../scea058a.pdf