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SN74HC574: SN74HC574 3.3V power supply consult

Lin_Charles
Expert 4260 points
Part Number: SN74HC574
Other Parts Discussed in Thread: SN74HCT574, SN74AHC574

Hi team,

I have one item to check with team. The datasheet say that the power supply should be 4.5V to 5.5V. So far My customer is using SN74HC574 with 3.3V voltage without any issue. They want to know why this device can also work as such lower supply? what performance may be effected?

BR,

Charles Lin

  • 0
    Guru 243820 points

    All HC family devices (including the '574) are designed for any supply voltage between 2 V and 6 V. The datasheet correctly specifies this.

    HCT devices have TTL-compatible inputs, and TTL runs only at 5 V, so specifiying a wider supply voltage range would not make sense.

    If the customer is using the SN74HCT574, then the electrical characteristics are not guaranteed at 3.3 V, and it should be replaced with the SN74HC574 (or better the SN74AHC574). In practice, only the input transistors have a modified switching threshold, and the rest of the circuit is probably the same between HC and HCT.

  • 0 in reply to Clemens Ladisch
    TI__Expert 4260 points

    Thanks. It is my mistake, customer is using  SN74HCT574 at 3.3V. I will let them change to HC or AHC family.