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Original question:

SN74AVC2T45: VCC under 1.2V

SN74AVC2T45: I/O with a different logic level to VCC

LI
Prodigy 10 points
Part Number: SN74AVC2T45
Other Parts Discussed in Thread: SN74AUP1T34, SN74AXC1T45

Hi guys,

    I want to know if you can help me to understand if this IC can tolerate and handle the input pins(B) has a different logic level than the voltage supplied through VCCB?.

Basically what I need, is to convert a protocol signal that has 1V logic into 3.3V, I don't have any 1.0V rail on my board, so I want to know if I can supply 1.2V into VCCB instead of the 1.0V that has my I/Os on 'B' side(please see the screenshot) and if this IC can support this configuration or not.

From my understanding VCCA and VCCB can go low as 1.2V, and the datasheet mentioned the I/Os pins can handle signals from -0.5V up to 4.6V, so I don't know if what I want to do with this IC is possible or not (without adding a 1V regulator to my board).

I never seen any of this before on any design(different voltage on VCCA/B than the one I'm having on that I/O) and from my understanding, VCC should be of the same level than the one I'm having on the I/O's Side, but eventhough I just want to confirm this with you guys...

Thanks.

  • 0
    Guru 272930 points

    The input signal will be recognized if it is above VIH. In this case, 0.65 × 1.2 V = 0.78 V.

    But as mention in the linked question, a 1.2 V supply with tolerances might be too low for the SN74AVC2T45.

    Devices like the SN74AUP1T34 or SN74AXC1T45 support lower voltages (and are smaller and cheaper).