Analog Clocking ICs Replace High-Frequency VCOs

The AD9552 oscillator frequency upconverter and the AD9547 clock synchronizer reduce implementation complexity and cost while improving jitter performance. The AD9552 replaces larger, expensive, high-frequency VCOs, including OCXO, VCXO, and TCXO devices. It requires either a single-ended low-frequency reference signal or a crystal reference to establish the higher output frequency the IC generates. Jitter is under 0.5 ps when operating with input frequencies in the range of 50 kHz to 80 MHz. The upconverter can generate almost any desired output frequency up to 900 MHz for a variety of applications, and consumes less than 400 mW in a 5-mm x 5-mm 32-lead LFCSP. The AD9547 provides synchronization for many systems, including synchronous optical networks (SONET/SDH). It generates an output clock that is synchronized to one of two differential or four single-ended external input references. The digital PLL allows for reduction of input time jitter or phase noise associated with the external references. The AD9547 continuously generates a clean (low jitter), valid output clock, even when all references fail, by means of digitally controlled loop and holdover circuitry. It comes in a 9-mm x 9-mm 64-lead LFCSP. In 1000-unit lots, pricing for the AD9552 and AD9547 is $7.65and $13.97, respectively. ANALOG DEVICES INC., Norwood, MA. (781) 329-4700.