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SN74LV1T34: dv/dt Range for SN74LV1T34

Xing He
Intellectual 2025 points
Part Number: SN74LV1T34
Other Parts Discussed in Thread: SN74AUP1T17

Hi  Experts,

My input signal with a low 17V/s slew rate for SN74LV1T34, does it will work normal? 

Thanks!

Best Regards,

Xing

  • 0
    TI__Mastermind 23373 points

    Hey Xing,

    Assuming this was a typo and you meant 17s/V and not V/s this would be too slow as you can see the max recommended spec for the input of this device is 20ns/V.
    Here's an FAQ that can explain further why such a slow CMOS input isn't recommended :
    [FAQ] How does a slow or floating input affect a CMOS device?

    You could resolve this with a schmitt-trigger input. What are the voltage ranges you'll be working with? The SN74AUP1T17 could work given that your output range is between 2.3 and 3.6V.

    If this wasn't a typo and 17V is actually being applied to the input, then this would exceed the abs max rating at the input by quite a bit. 

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    TI__Intellectual 2025 points

    Hi Rami,

    It was not a typo. The input will not reach 17V but in the device input range.

    I mean the slow rate is that the input will increase slow from 0 to 3V at a rate 17V/s.  Is that OK ?

    The max recommend spec id 20ns/V, so means the minimum dv/dt is 1/20 V/ns ?

    Best Regards,

    Xing

  • 0 in reply to Xing He
    TI__Mastermind 23373 points

    Xing,

    Oh okay, thanks for clearing that up.
    So yes, 20ns/V would be 1/20V/ns. So given your 17V/s that rate would be roughly 1/17 s/V or roughly 59ms/V, so a good bit out of spec.

    This would still be too slow. You would have oscillation and current spikes due to the shoot through current. The FAQ above explains this.
    You'll need a device with a schmitt-trigger to resolve this.

    -Rami