SPRUJD4A December 2024 – November 2025 AM62D-Q1
The ISO_LVL block provides electrical safety and functional correctness when the core domain is off and the battery-backed domain is on. A very low-power circuit detects if power is lost in the core domain and asserts an isolation signal which directs the cells in the ISO_LVL block to use the isolation tie-off values instead of trying to connect to the outputs from the powered-off circuitry.
However, because the power-loss-detection circuit must run with very low power, it cannot detect a loss of power early on in an uncontrolled power loss situation. A higher-power op-amp circuit would be needed to detect power loss earlier. Therefore, there is some possibility of invalid and metastable inputs being presented to the battery-backed domain through the ISO_LVL block in the case of an uncontrolled power loss situation. Data corruption in the battery-backed domain is prevented by the functional protection lockout circuit. The assertion of the isolation signal in this case prevents RTC from using too much power due to a short-circuit condition.