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SN74ALVC164245: Power-Up Sequence

Part Number: SN74ALVC164245
Other Parts Discussed in Thread: SN74LVC16T245,

I've the following power-up sequence:

The 3V3 is done by a LDO. Can I say, that the 3V3 on VCCA is powered up first and after a while the 5V on VCCB is also on its level - therefore powered up second?

Or do I have to do first switch on 3V3 (like a step) and then 5V (like a step) with a certain delay between these steps? If yes how much delay?

  • Hey Markus,

    Is this an accidental re-post or do you need some additional help? This seems to be identical to a former post that you've made here. If this is not accurate let me know and I can provide aid but it would appear that you've already got an answer that worked for you.

    Best Regards,

    Nick

  • The other post was for another part. Is the answer the same for all level-shifter?
  • Hello,

    Situation is the following: 5v0 (VCCB) goes through LDO and converts to 3v3 to power the VCCA (as described in the diagram of Markus).

    2 parts are under consideration:

    • SN74LVC16T245 (no power-up sequencing mentioned in datasheet)
      We have following statement: “this is one of the standard power-up scenarios through LDO for the translator devices and I do not anticipate any issues to the device with this”
    • SN74ALVC164245 (power-up sequencing must be followed)
      Is the same statement valid for SN74ALVC164245 as well?

    Thanks

    Best Regards,
    Martin

  • Hello Martin,

    Technically, VCCA should be up before VCCB for the ALVC164245. So it would be best if VCCB came later, but obviously that is impossible with an LDO configuration.

    It would probably be best to ensure all inputs are low on startup so that no excessive current is happening during startup. The device should be able to tolerate such a startup scenario, but there may be some additional current draw during startup.

    Best,
    Michael