zl30101 Zarlink Semiconductor, zl30101 Datasheet - Page 16

• Manufacturer Part Number: zl30101
• Description: T1/e1 Stratum 3 System Synchronizer
• Manufacturer: Zarlink Semiconductor

HMS=0: When the same ten Normal to Holdover to Normal mode changes occur and in each case Holdover mode
was entered for 2 seconds, then the overall MTIE would be 20 ns. As the delay value for the TIE corrector circuit is
not updated, there is no 13 ns measurement error at this point. The phase can still drift for 20 ns when the PLL is in
Holdover mode but when the PLL enters Normal mode again, the phase moves back to the original point so the
phase is not accumulated.
3.4
The DPLL of the ZL30101 consists of a phase detector, a limiter, a loop filter, a digitally controlled oscillator (DCO)
and a lock indicator, as shown in Figure 8. The data path from the phase detector to the limiter is tapped and routed
to the lock indicator that provides a lock indication which is output at the LOCK pin.
Phase Detector - the phase detector compares the virtual reference signal from the TIE corrector circuit with the
feedback signal and provides an error signal corresponding to the phase difference between the two. This error
signal is passed to the limiter circuit.
Limiter - the limiter receives the error signal from the phase detector and ensures that the DPLL responds to all
input transient conditions with a maximum output phase slope of 61 µs/s or 9.5 ms/s, see Table 1.
Loop Filter - the loop filter is similar to a first order low pass filter with a narrow or wide bandwidth suitable to
provide system synchronization or line card timing, see Table 1. The wide bandwidth can be used to closely track
the input reference in the presence of jitter or it can be temporarily enabled for fast locking to a new reference (1 s
lock time).
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TIE Corrector Circuit
13 ns is the maximum phase discontinuity in the transition from the Holdover mode to the Normal mode
when a new TIE corrector value is calculated
Digital Phase Lock Loop (DPLL)
Virtual Reference
from
Detector
Phase
Figure 8 - DPLL Block Diagram
Limiter
Zarlink Semiconductor Inc.
ZL30101
Control State Machine
State Select from
16
Loop Filter
Controlled
Oscillator
indicator
Digitally
Lock
Feedback signal from
Frequency Select MUX
Frequency Synthesizer
LOCK
DPLL Reference to
Data Sheet