To begin the design process, determine the following:

• Input voltage range
  • The supply voltage of the upstream device (device that is driving input pin A) will determine the appropriate input voltage range. For a valid logic-high, the value must exceed the high-level input voltage (V_IH) of the input port. For a valid logic low the value must be less than the low-level input voltage (V_IL) of the input port.
• Output voltage range
  • The supply voltage of the downstream device (device that output pin B is driving) will determine the appropriate output voltage range.