zl30101 Zarlink Semiconductor, zl30101 Datasheet - Page 17

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

Digitally Controlled Oscillator (DCO) - the DCO receives the limited and filtered signal from the loop filter, and
based on its value, generates a corresponding digital output signal. The synchronization method of the DCO is
dependent on the state of the ZL30101.
In Normal mode, the DCO provides an output signal which is frequency and phase locked to the selected input
reference signal.
In Holdover mode, the DCO is free running at a frequency equal to the frequency that the DCO was generating in
Normal mode. The frequency in Holdover mode is calculated from frequency samples stored 26 ms to 52 ms before
the ZL30101 entered Holdover mode.
In Freerun mode, the DCO is free running with an accuracy equal to the accuracy of the OSCi 20 MHz source.
Lock Indicator - the lock detector monitors if the output value of the phase detector is within the
phase-lock-window for a certain time. The selected phase-lock-window guarantees the stable operation of the
LOCK pin with maximum network jitter and wander on the reference input. If the DPLL is locked and then goes into
Holdover mode (auto or manual), the LOCK pin will initially stay high for 1 s. If at that point the DPLL is still in
holdover mode, the LOCK pin will go low; subsequently the LOCK pin will not return high for at least the full
lock-time duration. In Freerun mode the LOCK pin will go low immediately.
3.5
The output of the DCO is used by the frequency synthesizers to generate the C1.5o, C2o, C4o, C8o, C16o, C32o
and C65o clocks and the F4o, F8o, F16o, F32o and F65o frame pulses which are synchronized to the selected
reference input (REF0 or REF1). The frequency synthesizers use digital techniques to generate output clocks and
advanced noise shaping techniques to minimize the output jitter. The clock and frame pulse outputs have limited
driving capability and should be buffered when driving high capacitance loads.
3.6
As shown in Figure 1, the control state machine controls the TIE Corrector Circuit and the DPLL. The control of the
ZL30101 is based on the inputs MODE_SEL1:0, REF_SEL and HMS.
3.7
The ZL30101 can use either a clock or crystal as the master timing source. For recommended master timing
circuits, see the Applications - Master Clock section.
Frequency Synthesizers
State Machine
Master Clock
Zarlink Semiconductor Inc.
ZL30101
17
Data Sheet