Isolation circuit without routed path coupled to always-on power supply

An isolation circuit includes an inverter and a NOR-gate. The inverter includes an input terminal used to receive an input signal, an output terminal used to output an output signal according to the input signal, and a power terminal coupled to a power supply. The output signal is complementary to the input signal. The NOR-gate is used to perform a logic NOR operation using the output signal and an isolation control signal to generate a result signal. The NOR-gate includes a first input terminal coupled to the output terminal of the inverter for receiving the output signal, a second input terminal for receiving the isolation control signal, and an output terminal for outputting the result signal.