A first die is communicatively coupled to a first isolation communication channel and a second isolation communication channel and configured to send a first heartbeat signal over the first isolation communication channel. A second die is coupled to receive the first heartbeat signal from the first die over the first isolation communication channel and to supply a second heartbeat signal to the second isolation communication channel. The first die enters a first die low power mode responsive to detecting an absence of the second heartbeat signal and the second die enters a second die low power mode responsive to detecting an absence of the first heartbeat signal. The first and second die use low power oscillators in the low power mode to supply the heartbeat signals.