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Original question:

TXS0104E: Question on TXS0104/TXS0108E schematic

SN74AXC4T774: Question on SN74AXC4T774 OE connection

Jie Wang
Prodigy 100 points
Part Number: SN74AXC4T774
Other Parts Discussed in Thread: SN74CBTLV3257

On SN74AXC4T774 datasheet, it is said that  "/OE pin should be tied to VCCA  by a pull up to ensure the high-Z states during power-up or power-down".

We need the chip be enabled directly after the VCC powers up. So we tied /OE to GND directly. Is this OK?

I am trying to understand the risk here by connecting /OE to GND directly.  I understand that during power-up, the chip is active if /OE tied to GND directly.

But when the power goes up to a certain level, the chip will work normally, right? Is there any other risk here, like bus-contention risk here? 

The same question is also for SN74CBTLV3257.

Thanks very much

Jie Wang

  • 0
    Guru 316760 points

    When the supply voltage is above zero but below the recommended minimum of 0.65 V, the device is not guaranteed to work correctly, i.e., the outputs might drive a wrong value.

    The SN74CBTLV3257 is a passive switch, so the worst that can happen is that it makes a wrong connection. (At low voltages, the on-resistance will be higher.)