1# Phase Fault Monitoring 2 3## Overview 4 5Some voltage regulators contain redundant phases. If a redundant phase fails, 6the regulator can continue functioning normally. However redundancy has been 7lost, and the regulator may fail if another phase fails. 8 9Voltage regulators can be monitored for redundant phase faults. If a fault is 10detected, an error is logged on the BMC. 11 12When [regulator monitoring](monitoring.md) is enabled, the `phosphor-regulators` 13application checks for redundant phase faults every 15 seconds. 14 15A phase fault must be detected two consecutive times (15 seconds apart) before 16an error is logged. This provides "de-glitching" to ignore transient hardware 17problems. 18 19A phase fault error will only be logged for a regulator once per system boot. 20 21## How phase fault detection is defined 22 23Phase fault detection is defined for a voltage regulator using the 24[phase_fault_detection](config_file/phase_fault_detection.md) object in the 25[JSON config file](config_file/README.md). 26 27This object specifies actions to run, such as 28[i2c_compare_byte](config_file/i2c_compare_byte.md). 29 30## Error handling 31 32If a different type of error occurs while detecting phase faults in a regulator: 33 34- The error will be logged. If the same error occurs repeatedly on regulator, it 35 will only be logged once per system boot. 36- Any remaining actions for the regulator will be skipped. 37- Phase fault detection will continue with the next regulator. 38- Phase fault detection will be attempted again for this regulator during the 39 next monitoring cycle. 40