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SN74AVC2T45: Input signal higher than the port VCC

Juha Latvastenmaki
Prodigy 40 points
Part Number: SN74AVC2T45

Hi,

the customer uses the SN74AVC2T45 to level-shift the 1.8V JTAG  signals to the 3.3 V level and has therefore 1.8V (VCCA, always input) and 3.3V (VCCB, always output). Occasionally there can be a 3.3V input signal at the VCCA port, despite that the VCCA is 1.8V.

It wasn't 100% clear based on the datasheet if this is an acceptable scenario. Do you anticipate any challenges or issues if the input signal is higher than the input port VCC as described above?

Thanks, -Juha

  • 0
    TI__Guru* 97046 points

    Hi Juha,

    The inputs of this device are over-voltage tolerant to 4.6V, so this won't be a problem.

    Because the Absolute Maximum Ratings table lists a value that is not dependent on VCC for the maximum input voltage (4.6 V), the input can be driven above the VCC of 1.8 V without any problems. If the table listed something like 'VCC + 0.5 V' then there would be a problem.