LTC3374 Datasheet, PDF (16/24 Pages) Linear Technology – 8-Channel Parallelable 1A Buck DC/DCs

LTC3374
OPERATION
The LTC3374’s internal oscillator can be synchronized
through an internal PLL circuit, to an external frequency
by applying a square wave clock signal to the SYNC pin.
During synchronization, the top MOSFET/turn-on of buck
switching regulators 1 and 2 are locked to the rising edge
of the external frequency source. All other buck switching
regulators are locked to the appropriate phase of the ex-
ternal frequency source (see Buck Switching Regulators).
The synchronization frequency range is 1MHz to 3MHz.
After detecting an external clock on the first rising edge of
the SYNC pin, the PLL starts up at the current frequency
being programmed by the RT pin. The internal PLL then
requires a certain number of periods to gradually settle
until the frequency at SW matches the frequency and
phase of SYNC.
When the external clock is removed the LTC3374 needs
approximately 5µs to detect the absence of the external
clock. During this time, the PLL will continue to provide
clock cycles before it recognizes the lack of a SYNC input.
Once the external clock removal has been identified, the
oscillator will gradually adjust its operating frequency to
match the desired frequency programmed at the RT pin.
SYNC should be connected to ground if not used.
3374f
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