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SN74HCS125: advantage of /OE

Go
Genius 4165 points
Part Number: SN74HCS125

Hi,

TI has so many logic IC with low-enable function(like 125,240,244,245). 

Is there any specific reason that is still using low-enable ?

what is the advantage of Low-enable?

Thanks,

Go

  • +1
    Guru 258020 points

    This has purely historical reasons. Back in the time of TTL logic, NPN transistors were easier to fabricate than PNPs, so the outputs could strongly pull down but only weakly pull up. Therefore, it was preferrable to have active-low signals. Nowadays, it's just a convention.

  • +1
    TI__Genius 15370 points

    Hi Go,

    I thought I'd add on to the historical reasons Clemens gave:

    Having an active low enable also means you're consuming a little less power since you can just tie it to ground instead of VCC. Low-enable signals in general allow you to have control over when the device operates, especially during scenarios where you are ramping power to the device or really want to ensure that the device remains high impedance instead of giving a high/low output.

    Best,

    Malcolm