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SN74LVC1G11-EP: SN74LVC1G11-EP: VIH MIN WITH VCC=5V

Part Number: SN74LVC1G11-EP

Hello,

I am using SN74LVC1G11-EP component, my VCC voltage is 5V.

according to datasheet the VOH MIN is 3.8V and it ok with my design.

but the VIH MIN is 0.7*VCC it means 0.7*5V=3.5V.

if my inputs are working with 3.3V and 3V voltages-maximum and the VIH MIN of the component is 3.5V,

I think I have problem with the design, I produced a lot of boards of this type and it working without problems yet  (:

How is it possible? Maybe this component working with VIH MIN of 2V?  why didn't I recognize it as a failure at my system tests?

Are you think that there is any risk and I need to re-layout this board again? Do you have replacement for this component with VCC=5V and VIH MIN=2V?

This board belong to aircraft system and I need high level of safety.

Thanks,

Igal

  • Igal,
    I agree with your assessment. This will not be a robust design. The VIH/VIL values are chosen to work across wide range of variables for temperature and process. For a nominal device the actual vih/vil levels will be somewhat closer to 0.6VCC and 0.4VCC and will vary somewhat with temperature. All devices will be somewhat different, but will fit within the values specified in the recommended operating conditions. Noise on supplies could also affect any margin for VIH.

    I am not certain what your minimum VIH will be from your statements above. 3V, 3.3V, or 2V?

    You need a device that operates on TTL input levels to get a VIH of 2V.
    This parametric list has all the 3 input AND gates with 2V input levels.
    Unfortunately, they all are triple 3 input, and much larger packages.
    www.ti.com/.../gate-products.page
    You may have other constraints as well to satisfy. Temp, voh/vol loading, ...

    Powering the LVC1G11 at a lower voltage could also be a solution. You would need to verify specific requirements with VIH/VIL VOH/VOL for voltage chosen and loading.
    Regards,
    Wade
  • I need inputs for 3.3V and output with 5V, that why I powered with VCC=5V.

    but someone that did the design missed the inputs voltage levels.