AD9549 manufactured by Analog Devices provides extended holdover functionality and jitter cleanup to increase system stability and maximize network uptime. The AD9549 is the first IC of its kind to integrate DDS technology, an element necessary to enabling such narrow loop filter bandwidths and switchover with extended holdover capability functions.
Analog Devices' AD9549 dual-input network clock generator provides networking and data communications systems designers with a new standard of performance to maximize network uptime and increase system stability and reliability. Using a new architecture based on ADI's proprietary DDS (direct digital synthesis) technology, the AD9549 enables a more stable holdover, allowing designers additional time to restore the clock reference in the event of a failure. If an input reference clock fails, the clock generator IC continues to "hold" the output frequency until the reference failure is recovered. With the AD9549 there is no time limit to holdover - the output would be maintained until the system is powered down or a new reference is provided. Compared to competitive solutions, this holdover functionality improves stability by as much as two orders of magnitude (~0.37 ppm vs. ~30 ppm), resulting in significantly increased system uptime.
The AD9549 features A and B reference inputs with switchover. This feature enables a system output clock to maintain operation in the event the primary reference clock fails. It also enables users to set loop bandwidth to optimize reference-A-to-reference-B switching time. It reduces jitter to 600 fs (femto seconds), 25 percent better than competing devices. The AD9549 has a programmable digital loop filter capable of bandwidths down to 1 Hz and below.
Additionally, the AD9549 provides flexible output frequency options, enabling system designers for non-networking applications to avoid additional frequency translation circuitry. It could be used to create a complete clock path when combined with Analog Devices' AD951x family of clock distribution ICs and ADI's high-speed AD9445/6/7 analog-to-digital converters.