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SN74AUP1G125: OE Thrshold at Vcc = 2.9V

Russell Wetherley1
Expert 4255 points
Part Number: SN74AUP1G125
Other Parts Discussed in Thread: SN74LV1T125

Hello E2E,

I am posting on behalf of a customer. 

We are operating with Vcc at 2.9v  We would like to pull OE up to 1.8V which is close to the MIN.  Do you have any data on how much buffer there is below the MIN?  I did a test in the lab and found the threshold at 1.3V but I am not sure what the part to part variation would be.

Now, I understand that we can't guarantee operation outside of spec of the datasheet, but table 6.3 conveniently doesn't take data at 2.9V... If we assume worst case (Vcc = 3.0V), then they won't eclipse the necessary OE threshold.  But if Vcc = 2.7V, then they will pass our datasheet spec.  So, do we have data at 2.9V?  Will their above conditions work?

Finally, I did warn them about the following from the DS: 

To assure the high-impedance state during power up or power down, OE must be tied to VCC through a pullup resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.

 


Thanks for the help!

Russell

  • 0
    TI__Mastermind 45815 points
    Hi Russell,

    I think you answered your own question here. If Vcc = 3 V then they won't meet the spec and if Vcc = 2.7 V then it will meet spec. This is all with the assumption that the 1.8 V rail is ideal and not significantly less (there will be some voltage drop due to the pull-up resistor and leakage current of the device). There's also the issue of the variation in power up sequencing (e.g. if the 2.9 V rail powers up quicker than the 1.8 V rail then the OE input could be below the Vih min spec during that whole process). I don't understand the need to use the 1.8 V rail and not the 2.9 V rail.

    Unfortunately, we don't have any data for 2.9 V supply. The threshold typically is around 1/2 Vcc (with variation across PVT), so they could potentially get away with doing this but like you said it wouldn't be something we could guarantee to work.
  • 0 in reply to Dylan Hubbard
    TI__Expert 4255 points

    Thanks Dylan,

    Do you know of any similar devices where  2.9Vcc and 1.8 (coming from GPIO) would work?

    Thanks!

    Russell

  • 0 in reply to Russell Wetherley1
    TI__Guru* 97046 points
    Hey Russell,
    You could use SN74LV1T125 instead - same basic functionality, designed for translation.