[FAQ] What is the logic state of a digital isolator with no input signal?

When the input channel of a digital isolator is unpowered or the pins left floating, its respective output pin takes a predefined state (called the default state or failsafe state) which can be either LOW or HIGH depending on the device chosen. The suffix ‘F’ in a device’s part number indicates the default state of output channels of the isolator. For example, no ‘F’ in the part number ISO7721DWR indicates that the default state for this device is HIGH. Similarly, the ‘F’ in ISO7721FDWR indicates that the default state for this device is LOW. Read Device Functional Modes for more information.