The oscillator can be synchronized to external clock (SYNC IN) or output a clock to synchronize other devices (SYNC out) on the SYNC pin. To support phase shifted clock for both multi-rail interleaving and multi-phase operation, the internal oscillator can be phase-shifted from the SYNC pin by 0, 90, 120, 180, 240, or 270 degrees for 1, 2, 3, or 4 phase operation. The SYNC IN or SYNC OUT function, and phase position of single phase or stand-alone devices can be selected by pin-strapping through resistor divider on at the ADRSEL pin, or by the resistor from the MSEL2 pin to AGND for multi-phase loop follower devices.

In single output multi-phase stack configurations, the SYNC phase offset is programmed along with device count and phase position using the MSEL2 pin. Loop follower devices in multi-phase stacks are always configured as SYNC_IN while the loop controller device can be configured for auto-detect, SYNC_IN, or SYNC_OUT through the resistor divider on the ADRSEL pin.

After initial power up and pin detection, if SYNC IN/OUT is set as auto-detection configuration, the TPS546D24S senses the SYNC pin to determine if there is any external SYNC clock. Switching or a consistent pullup on the SYNC pin sets the device for SYNC_IN while a consistent pulldown on SYNC sets the device for SYNC_OUT. The TPS546D24S devices programmed to be loop followers are always programmed to be SYNC IN.

When configured for SYNC_IN, if SYNC input pulses are missed for two cycles, or the oscillator frequency drops below 50% of the free-running switching frequency, the device determines that SYNC clock is lost. If the TPS546D24S is part of a multi-phase stack, the converter shuts down and remains disabled until a SYNC signal is reestablished to prevent damage due to the loss of synchronization. Single phase stand-alone devices continues to operate at approximately 50% of the nominal frequency.