US Patent 11442108 Isolation logic test circuit and associated test method

A circuit includes: a first power domain including: an isolation cell, a first selection circuit having inputs for receiving a first functional signal and a first test signal and an output for controlling the isolation cell, and a second selection circuit having inputs for receiving a second functional signal and a second test signal and an output coupled to a signal input of the isolation cell; a second power domain including: a first circuit having an input coupled to a signal output of the isolation cell, a first observation element coupled to the signal output of the isolation cell, and a second observation element coupled to an output of the first circuit; where, when in test mode, the first selection circuit controls the isolation cell based on the first test signal, and the second selection circuit provides the second test signal to the signal input of the isolation cell.