Measures of Performance 19
January 11, 2017
82V3155 ENHANCED T1/E1/OC3 WAN PLL WITH DUAL REFERENCE INPUTS
3.10 MAXIMUM TIME INTERVAL ERROR (MTIE)
MTIE is the maximum peak to peak delay between a given timing
signal and an ideal timing signal within a particular observation period.
3.11 PHASE CONTINUITY
Phase continuity is the phase difference between a given timing
signal and an ideal timing signal at the end of a particular observation
period. Usually, the given timing signal and the ideal timing signal are of
the same frequency. Phase continuity applies to the output of the
synchronizer after a signal disturbance due to a mode change. The
observation period is usually the time from the disturbance, to just after
the synchronizer has settled to a steady state.
In the case of the IDT82V3155, the output signal phase continuity is
maintained to within ±5 ns at the instance (over one frame) of all mode
changes. The total phase shift, depending on the type of mode change,
may accumulate up to 200 ns over many frames. The rate of change of
the 200 ns phase shift is limited to a maximum phase slope of
approximately 5 ns per 125 µs. This meets the AT&T TR62411
maximum phase slope requirement of 7.6 ns per 125 µs and Telcordia
GR-1244-CORE (81 ns per 1.326 ms).
3.12 PHASE LOCK TIME
This is the time it takes the synchronizer to phase lock to the input
signal. Phase lock occurs when the input signal and output signal are
not changing in phase with respect to each other (not including jitter).
Lock time is very difficult to determine because it is affected by many
factors including:
1. Initial input to output phase difference
2. Initial input to output frequency difference
3. Synchronizer loop filter
4. Synchronizer limiter
Although a short lock time is desirable, it is not always possible to
achieve due to other synchronizer requirements. For instance, better
jitter transfer performance is achieved with a lower frequency loop filter
which increases lock time. And better (smaller) phase slope
performance (limiter) results in longer lock times. The IDT82V3155 loop
filter and limiter are optimized to meet the AT&T TR62411 jitter transfer
and phase slope requirements. Consequently, phase lock time, which is
not a standard requirement, may be longer than in other applications.
See “7.1 Performance”for details.
The IDT82V3155 provides a FLOCK pin to enable the Fast Lock
mode. When this pin is set to high, the DPLL will lock to an input
reference within approximately 500 ms.
