SN74LVC821A: Output Voltage

Angad Shah

Part Number: SN74LVC821A

Support Path: /Product/Help with Device Selection/

Hi All,

I am using the aforementioned Part (SN74LVC821ADGVR) for my design. I have a doubt in Output voltage parameters mentioned in Datasheet.

The Datasheet says Vo in 3-State will be 5.5V, whereas the Vcc provided is 3.6 (Max). How is this possible. Please explain. I guess it could be a probable typo but would like to get clarifications before I freeze on to this part.

Regards

Angad Shah.

over 8 years ago

0 Clemens Ladisch over 8 years ago

Guru 317150 points

That specification is not the voltage that the pin has (a 3-stated pin is floating), but the voltage that you are allowed to apply to the pin.

This device is designed to be connected to a bus; that specification means that other devices on the bus are not allowed to drive more than 5.5 V.

0 Angad Shah over 8 years ago in reply to Clemens Ladisch

Prodigy 175 points

Hi,

Thanks for the quick response.

Yes you are right, that stands true for the Input to the device. But my doubt is on the output side. The datasheet says output can be between 0-5.5V when in 3-state (Floating).

This is what I am not very clear about.

PFA.

Regards

Angad Shah

0 Clemens Ladisch over 8 years ago in reply to Angad Shah

Guru 317150 points

No, that is not what it says. A "recommended operating condition" is not about how the device itself behaves, but about what your circuit is allowed to do to the device. In this table, V_O is the voltage that your circuit applies to the pin. It is called "output voltage" because it is applied to a pin that is called "output".

0 Angad Shah over 8 years ago in reply to Clemens Ladisch

Prodigy 175 points

That means if this device is connected to a Bi-directional bus where multiple device are driving data sequentially then some other device can drive upto 5.5V on this bus without damaging this device while its in 3-state mode. Correct me if i got it wrong.

0 Clemens Ladisch over 8 years ago in reply to Angad Shah

Guru 317150 points

Yes.

0 Angad Shah over 8 years ago in reply to Clemens Ladisch

Prodigy 175 points

Thank you very much for spontaneous response. This helped a lot.

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SN74LVC821A: Output Voltage