The AD9520 and AD9522 multi-output clock generation and distribution ICs from Analog Devices Inc. include a 512-byte embedded EEPROM memory block, affording system engineers a programmable clock solution that can serve as both the source and system clock. By programming a specific set of output conditions using the on-chip memory, designers can easily configure the AD9520/2 as the source clock to ensure initial processing functions are synchronized when the system is powered on or reset.

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In addition to the on-chip EEPROM and phase-locked loop (PLL), the AD9520/2 integrate dividers, fanout buffers, and a voltage-controlled oscillator (VCO) that tunes from 1.4 to 2.95 GHz. An external 3.3/5-V voltage-controlled crystal oscillator (VCO/VCXO) of up to 2.4 GHz also can be used. The PLL/VCO clock-generation circuitry boasts industry phase noise of –150 dBc/Hz at a 10-kHz offset on a 200-MHz clock signal, while the clock distribution fanout channels feature ultra-low wideband jitter performance of 225 fs.

Two reference inputs allow glitch-free switchover for applications requiring redundant references, while a PLL holdover mode maintains the output frequency in the event of a lost reference signal. Zero-delay operation is available to ensure precise phase alignment between inputs and outputs. The AD9520 offers 12 differential low-voltage positive emitter-coupled logic (LVPECL) outputs in four groups, each with a 1-to-32 divider and phase delay. The AD9522 includes 12 differential low-voltage differential signaling (LVDS) outputs. Both devices alternatively offer up to 24 single-ended CMOS output configurations up to 250 MHz.

The AD9520 is available now in production quantities. The AD9522 is available for sampling and will be released in October. The devices come in a 64-lead lead-frame chip-scale package (LFCSP) and cost $12.65 each in 1000-unit quantities.

• Analog Devices
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