• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Subscribers 18 subscribers
  • Views 771 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN74LVC2G14-Q1: VIH & VIL minimum and maximum value calculate

user6365074
Prodigy 110 points
Part Number: SN74LVC2G14-Q1

Hello,

I'm using the IC for relaxation oscillator, and I want to calculate the tolerance of my circuit. 

Operate temperature is -40 degrees to 125 degrees

Operate VCC = 4.9V to 5.1V, 

so is there any formula or curve relation of temperature with VIH and VIL?

and How is the minimum and maximum value definition? VCC tolerance or Temperature

My calculation is in the figure shows that there have the same value in minimum value in -40 degrees to 85 degrees & -40 degrees to 125 degrees

so I assume the minimum value is in -40 degrees and maximum value in 85 degrees and 125 degrees, and using interpolation to get the correspond value in different VCC

Thanks for apply.

  • 0
    Guru 243090 points

    Temperature variations affect the two complementary transistors in the input in a similar way, so I'd guess that the threshold tolerances are mostly determined by manufacturing variations. In other words: you will not be able to get tighter tolerances.

    A logic device like this is designed to handle digital signals (and the Schmitt trigger handles digital signals with slow edges). If you need any accuracy in the switching threshold (or its hysteresis), you need to use a comparator instead.

  • 0 in reply to Clemens Ladisch
    Prodigy 110 points

    Hello ,

    I have another question,

    I have heat the schmitt trigger to see the VIH and VIL change,

    and when the temperature become higher , VIH and VIL will become larger,

    so is that can support the assume

    when the temperature is high, VIH and VIL ==> larger ==> Maximum value

    when the temperature is low, VIH and VIL ==> smaller ==> Minimum value

    Thanks for apply

  • 0 in reply to user6365074
    Guru 243090 points

    A MOSFET's RDS(ON) increases with temperature. Apparently, in your device, the N-channel and P-channel transistors are affected by a different amount (which might be related to the Pch's greater size), but TI will not guarantee this in any way. You can attempt to measure this effect, but you cannot know how much future devices will deviate from your measurements.

  • 0 in reply to Clemens Ladisch
    Prodigy 110 points

    Hello Clemens Ladisch,,

    There is some information In the datasheet of SNx4LS14,
    there have the curve of temperature vs VIH and VIL,

    so is that similar to SN74lVC2G14-q1 characteristic of VIH and VIL?
    Or maybe TI have the curve but not show in the datasheet which can offer ?
    Thanks for apply

  • 0 in reply to user6365074
    Guru 243090 points

    The LS family is based on BJTs and has an entirely different input structure.

    Apparently, TI does not provide this information for CMOS devices.