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In what sequence should I turn on and off the power and input signals?

The following figure shows the I/O-equivalent circuit of the TC74HC/HCT series.

[Figure: input/output equivalent circuit of TC74HC/HCT]

To meet the absolute maximum ratings, the power-on sequence must be as follow: (1) GND, (2) Vcc, (3) input signals. For the power-off sequence, perform the power-on sequence in reverse order.

Input-tolerant devices (i.e., devices that do not have a diode in the forward direction from inputs to the power source) such as TC74VHC/VHCT, TC74LCX and TC74VCX can accept input signals even when no power is supplied. Therefore, the order of (2) and (3) is not significant. However, the absolute rated input diode current (IIK) must not be exceeded.
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