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

Input/Output Equivalent Circuit of TC74HC/HCT
Input/Output Equivalent Circuit of TC74HC/HCT

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

To meet the absolute maximum ratings, the power-on must be as follows

(1) Connect GND
(2) Connect VCC (ON)
(3) Connecting Input Signals (Turning On)

If the input signal is input first, an unnecessary current may flow to the input in an IC without the input tolerant function, which may damage the IC or equipment.
For the power-off sequience perform the power-on sequence in reverse order.
Products with an input tolerant function such as TC74VHC/VHCT,TC74LCX,TC74VCX (no input protective diode for forward direction from input to power supply) can apply an input signal even when power is not applied. Therefore, the loading sequence of (2) and (3) is not required.

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