Is any more information available about using the LTC3407-2 in externally synchronized mode by feeding a clock signal to the MODE/SYNC pin? A general description of the synchronization mechanism would help answer several questions...
Specific questions:
- The synchronization frequency f_sync is described as "2.25 MHz typical" in the datasheet, with no minimum or maximum. What is the acceptable synchronization range?
- What is the allowable cycle-to-cycle variation in f_sync period? I'm looking at using a LTC6908-1 spread-spectrum oscillator (+/- 10% spreading nominal, 12.5% max); is this acceptable?
- I'm used to regulators where external synchronization requires the sync frequency to be faster than the set frequency; for this part, the sync frequency is right in the middle of the set frequency range. How does the part detect the presence of a sync signal, and what is the behavior if the sync signal appears (due to slow oscillator startup) or disappears (due to fault) after the regulator is already operating?