SN74LV4T125: Recommended OE pin connection

Gerald Dalum

Prodigy 80 points

Part Number: SN74LV4T125

After looking at the datasheet for the SN74LV4T125,

I do not see too much on the explanation of the OE pin.

Are the options to connect to GND or VCC?

What are the differences?

What scenarios would call for connecting to one or the other?

over 2 years ago

0 Albert Xu1 over 2 years ago

TI__Mastermind 22355 points

Hi Gerald,

You can see this FAQ: [FAQ] How does a slow or floating input affect a CMOS device? for why we want to connect an unused OE pin to GND or VCC.

If the channel is unused, it doesn't matter which one (GND/VCC) you connect to. Generally, which ever is easier will be what customers will prefer to use.

0 Gerald Dalum over 2 years ago in reply to Albert Xu1

Prodigy 80 points

Yes, the datasheet explains that for unused inputs, we connect to GND or VCC. I really wanted to understand the OE pins, not the unused input pins.

0 Albert Xu1 over 2 years ago in reply to Gerald Dalum

TI__Mastermind 22355 points

Hi Gerald,

OE pins will also follow the requirements that are stated for unused inputs, as the OE pin is an input itself.

I may be misunderstanding your question a bit, and I apologize. If you are just asking about the OE pin function, this is an inverted input. You will set to high to disable the output and low to enable the output.

0 Gerald Dalum over 2 years ago in reply to Albert Xu1

Prodigy 80 points

Yes, I was just asking about the OE pin function. Thanks for the clarification. I believe I understand now based off of your answer.

To clarify, Lets say I am going to translate 5v into 3.3V on 3 of the 4 channels, and will not be using 1 channel.

1. I will connect 3.3V to vcc
2. On the 3 enabled channels, I will set LOW to the OE pins.
3. On the 1 disabled channel, I will connect GND to its input pin and set HIGH to its OE pin.

+1 Albert Xu1 over 2 years ago in reply to Gerald Dalum

TI__Mastermind 22355 points

Yep, that sounds good!

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SN74LV4T125: Recommended OE pin connection