Attempts to write (E4h) MFR_SPECIFIC_E4 (SYNC_CONFIG) to any value outside those specified as valid are considered invalid or unsupported data and cause the TPSM8D6C24 to respond by flagging the appropriate status bits and notifying the host according to the PMBus 1.3.1 Part II specification section 10.9.3.

When SYNC_DIR = 11b - Enable Auto Detect, the TPSM8D6C24 selects SYNC_IN or SYNC_OUT based on the state of the SYNC pin when the Enable condition, as defined by ON_OFF_CONFIG, is met. If the SYNC_PIN is > 2 V or switching faster than 75% of FRQUENCY_SWITCH, SYNC_IN is enabled. If the SYNC_PIN is less than 0.8 V and not switching, SYNC_OUT is selected.

Loop follower devices in a multi-phase stack are always configured for SYNC_IN and declare a SYNC_FAULT in (80h) STATUS_MFR_SPECIFIC if enabled before a SYNC signal is present, or if SYNC is lost before being disabled. To prevent such false SYNC_FAULTs from occurring, it is recommended that multi-phase stacks configure select SYNC_OUT in (E4h) MFR_SPECIFIC_20 (SYNC_CONFIG) if not using an external synchronization signal.

Changing SYNC_DIR from SYNC_IN to SYNC_OUT while enabled and operating at the lower limit of the SYNC_IN function (70% of nominal switching frequency) results in the switching frequency remaining at the lower limit of SYNC_IN until the output is disabled and enabled.

Changing SYNC_DIR from SYNC_IN to SYNC_OUT on a multi-phase stack while conversion is enabled but prevented due to a SYNC_FAULT will result in the internal oscillator operating at 70% of its nominal frequency. Since this is outside of the compliant SYNC_IN range of the loop follower device, this can result in unsynchronized operation.