Low-jitter, programmable frequency translator generates eight outputs

October 17, 2013 // By Julien Happich
IDT’s 8T49N28x family of universal frequency translator devices, generates eight different output frequencies with less than 300 femtoseconds RMS phase jitter over the standard 12 kHz to 20 MHz integration range, in one chip.

The mixed signal devices offers eight independently-programmable clocking outputs with the flexibility to apply virtually any input frequency and select virtually any output frequency.

The 8T49N28x devices are available with one or two PLLs in a single package, depending on the needs of the application. When configured as a frequency synthesiser , the device can use a low-cost, readily-available 10 to 40MHz crystal to produce any frequency from 8kHz to 1.0GHz, regardless of the crystal frequency used. In a frequency translator configuration, the devices accept up to four input reference clocks per PLL from 8 kHz to 875 MHz, switching between them as necessary to generate any output frequency from 8 kHz to 1.0 GHz. These multiple inputs can also be used for redundancy purposes. Each output is individually programmable as LVPECL, LVDS, or as a pair of LVCMOS signals.

The chip’s integrated fractional output divider has been improved through architectural changes in the analogue domain to be able to generate independent clock frequencies with less than 0.7 psec of RMS jitter.

IDT is also a provider of MEMS-based oscillators supporting 100 femtosecond (0.1 psec) typical phase jitter performance, so in the future the company could deliver System-in-Package solutions combining the clock sources and the frequency translators.

“A combined solution is definitely on our road map and it would certainly bring a cost advantage”, said Director of System Architecture, Ian Dobson, “though most of our customers in the telecoms market are fairly conservative and are not ready to adopt our MEMS-based technology, they would rather combine our frequency synthesiser chips with external crystal oscillators... we’ll leave the option of designing with crystal oscillators open”.

To exploit the flexibility of the devices, the Timing Commander software tool offers a complete view of the device’s internals, with easy to fill blanks to choose your input and output frequencies, with contextual menus and design help at hand. Designers can then view the phase noise plot