[time-nuts] AD9548 - Clock IC Generates Up to 400 MHz from 1 PPS GPS Signal

christopher hoover ch at murgatroid.com
Thu Jun 11 00:25:37 EDT 2009

[fyi -- this may be of general interest, but n.b. that this A.D. 
marketing - ch]

Clock IC Generates Up to 400 MHz from 1 PPS GPS Signal

The AD9548 
is the first clock chip in the industry to directly generate up to a 400 
MHz output clock, with extremely low phase noise, that is locked to a 
standard one pulse-per-second (PPS) GPS clock signal. This performance 
is a result of combining Analog Devices' proprietary direct digital 
synthesis (DDS) technology with a state-of-the-art digital phase-locked 
loop (DPLL). Other solutions for synchronizing to the GPS 1 PPS source 
typically rely on one or more frequency upconversion steps. Maintaining 
low output noise, while providing over eight orders of magnitude of 
frequency scaling (1 Hz input to over 100 MHz output), is a significant 
challenge. The AD9548 is able to mitigate this effect thanks to a 
digital loop filter capable of bandwidths as low as 1 MHz (10 Hz to 3 Hz).


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