Tell me about the input tolerant function.

Input/output equivalent circuit and specifications of input/output allowable voltage are shown below:

The input tolerant function is a function to prevent current from input to the power supply when the input is set higher than the power supply voltage or when power supply VCC = 0V.

The specification of the allowable input voltage is described in the input voltage of recommended operating conditions. When input/output specification is 0 - VCC, voltage that exceeds VCC cannot be applied because the circuit has a diode.

The input voltage of VHC/LCX is 0 - 5.5V (with input tolerant function), so voltage up to 5.5V can be applied to input regardless of the power supply voltage. When the power supply voltage VCC = 3.3V, level conversion from 5V to 3.3V is available.

The input voltage of VCX is 0 - 3.6V (with input tolerant function), so voltage up to 3.6V can be applied to input regardless of the power supply voltage. When the power supply voltage VCC = 1.8V, level conversion from 3.3V to 1.8V is available.

Input/output equivalent circuit and specifications of allowable input/output voltages
tolerant function Both input/output input only Neither input/output
series VHCT,LCX,VCX VHC,LVX AC/ACT,HC/HCT
input/output equivalent circuit
allowable input voltage operating 0 - 5.5V (VCX 3.6V) 0 - 5.5V (VCX 3.6V) 0 - VCC
Power down 0 - 5.5V (VCX 3.6V) 0 - 5.5V (VCX 3.6V) 0V (voltage cannot be supplied)
allowable output voltage output enable 0 - VCC 0 - VCC 0 - VCC
output disable 0 - 5.5V (VCX 3.6V) 0 - VCC 0 - VCC
Power down 0 - 5.5V (VCX 3.6V) 0V (voltage cannot be supplied) 0V (voltage cannot be supplied)
Recommended Operating Conditions in the Data Sheet
Item Symbol
(Unit)
Rating Remarks
TC74VHC TC74LCX TC74VCX
Power supply voltage VCC
(V)
2 - 5.5 2 - 3.6 1.65 - 3.6  
Input voltage VIN
(V)
0 - 5.5 0 - 5.5 0 - 3.6 With input tolerant function
Output voltage VOUT
(V)
0 - VCC 0 - 5.5
(Note 1)
0 - 3.6
(Note 1)
LCX and VCX: with output tolerant function
0 - VCCA
(Note 2)
0 - VCCA
(Note 2)
  • Note 1: output HZ
  • Note 2: output "H" or "L"

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