User`s guide

User’s Guide ADI-8 QS © RME
53
16.9 SteadyClock
The SteadyClock technology of the ADI-8 QS guarantees an excellent performance in all clock
modes. Its highly efficient jitter suppression refreshes and cleans up any clock signal, and pro-
vides it as reference clock at the word clock output.
Usually a clock section consists of an analog PLL for external synchronization and several
quartz oscillators for internal synchronisation. SteadyClock requires only one quartz, using a
frequency not equalling digital audio. Latest circuit designs like hi-speed digital synthesizer,
digital PLL, 100 MHz sample rate and analog filtering allow RME to realize a completely newly
developed clock technology, right within the FPGA at lowest costs. The clock's performance
exceeds even professional expectations. Despite its remarkable features, SteadyClock reacts
quite fast compared to other techniques. It locks in fractions of a second to the input signal,
follows even extreme varipitch changes with phase accuracy, and locks directly within a range
of 28 kHz up to 200 kHz.
SteadyClock has originally been de-
veloped to gain a stable and clean
clock from the heavily jittery MADI data
signal. The embedded MADI clock
suffers from about 80 ns jitter, caused
by the time resolution of 125 MHz
within the format. Common jitter values
for other devices are 5 ns, while a very
good clock will have less than 2 ns.
The picture to the right shows the
MADI input signal with 80 ns of jitter
(top graph, yellow). Thanks to Steady-
Clock this signal turns into a clock with
less than 2 ns jitter (lower graph, blue).
Using the other input sources of the
ADI-8 QS, word clock, ADAT and
AES/EBU, you'll most probably never
experience such high jitter values. But
SteadyClock is not only ready for them,
it would handle them just on the fly.
The screnshot to the right shows an
extremely jittery word clock signal of
about 50 ns jitter (top graph, yellow).
Again SteadyClock provides an ex-
treme clean-up. The filtered clock
shows less than 2 ns jitter (lower
graph, blue).
The cleaned and jitter-freed signal can be used as reference clock for any application, without
any problem. The signal processed by SteadyClock is of course not only used internally, but
also available at the ADI-8 QS's word clock output. It is also used to clock the digital outputs
MADI, ADAT and AES/EBU.