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.

SN74LVC00A-Q1: 5V supply allowed?

Genius 12495 points
Part Number: SN74LVC00A-Q1
Other Parts Discussed in Thread: SN74AHC00, SN74LVC1G00, SN74AHC00-Q1, SN74LVC1G97-Q1

Hello Team,

according to the data sheet recommended Vmax =3.6V and max current for all channels = 50mA, correct?

If applying 5V supply and reducing the current per channel to 9mA this will result in the same power dissipation. Can the part be used under these conditions without any reliability issues, please?

Thanks and Best Regards,

Hans

  • Hi Hans,

    This device has a recommended supply voltage of up to 3.6V. Operating at a higher voltage is possible but will reduce reliability as all the datasheet specs are tested with a voltage supply up to 3.6V. I would recommend using the SN74HCS00-Q1. This device supports up to a 6V supply and can handle up to 35mA per channel.

    Regards,

    Sebastian

  • Hi Sebastian, I guess the 3.6V limit for SN74LVC00A-Q1 is the power dissipation. So with 3.6V and a max current of 50mA this results in 180mW for the IC. If I reduce the current to <=9mA per channel at a supply voltage of 5V I calculate 4·9mA·5V = 180mW which meets the above power limit.

    May I kindly ask you to check if this assumption and calculation is correct, please?

    Thanks and Best Regards, Hans

  • No, this is not related to power dissipation. Increasing the supply voltage actually decreases VOL and thus the power dissipated inside the device.

    When you exceed any of the recommended operating conditions, none of the electrical characteristics are guaranteed. Also see the linked question.

    Why do you want to use an LVC device? What is the actual problem you're trying to solve?

  • Hi Clemens, this is part of a functional safety application and the inputs could stay high (5V) when supply is switched off. As far as I know this is not allowed for SN74HCS00 and SN74AHC00, correct? 

    LVC is the only family which allows Vin to be greater Vcc, right? Why is the SN74LVC1G00 specified for Vcc=1.65...5.5V but the SN74LVC00 just for 3.6V while both have identical abs max ratings of up to 6.5V? 

    When limiting the output current to max 1mA per channel I am pretty sure that it does not impact reliability.

    Thanks and Best Regards, Hans

  • AHC inputs are overvoltage tolerant; the SN74AHC00-Q1 is exactly what you want. If you need fewer than four gates, consider the SN74LVC1G97-Q1.

    The absolute maximum ratings tell you where the device will not be damaged. The recommended operating conditions tell you where the device will work correctly. Large LVC devices are not specified for 5 V because they do not work correctly at 5 V.

  • Thank you, Clemens!