SN74ACT244: SN74ACT244 operates in 3V~4.5V VCC

Lenna Yan

Intellectual 1960 points

Part Number: SN74ACT244
Other Parts Discussed in Thread: SN74AC244

Hi expert,

The normal operation voltage for SN74ACT244 is 4.5V~5.5V. Could you tell what the state of the output stage will be if the VCC is 3V~4.5V?

over 5 years ago

0 Clemens Ladisch over 5 years ago

Guru 256060 points

The ACT family is designed for compatibility with 5 V TTL voltage levels. If the supply voltage is lower than specified in the recommended operating conditions, there is no guarantee whatsoever.

If you want to use any other voltage level, use AC instead, i.e., SN74AC244.

(In practice, the AC and ACT outputs are pretty much identical; the problem with running ACT at less than 4.5 V is that the input switching thresholds will be unspecified.)

0 Lenna Yan over 5 years ago in reply to Clemens Ladisch

TI__Intellectual 1960 points

Hi Clemens,

Thank for your quick reply. Can I understand the output is uncertain if the VCC is 3V~4.5V?

0 Clemens Ladisch over 5 years ago in reply to Lenna Yan

Guru 256060 points

As I said, there is no guarantee. In practice, it will be either low or high (or maybe oscillating if the inputs are invalid; see [FAQ] How does a slow or floating input affect a CMOS device?).

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SN74ACT244: SN74ACT244 operates in 3V~4.5V VCC