zl30101 Zarlink Semiconductor, zl30101 Datasheet - Page 13

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

The precise frequency monitor’s failure thresholds are compatible with Telcordia GR-1244-CORE Stratum 3 as
shown in Figure 5. It will take the precise frequency monitor up to 10 s to qualify or disqualify the input reference.
3.3
The TIE corrector circuit eliminates phase transients on the output clock that may occur during reference switching
or the recovery from Holdover mode to Normal mode.
On recovery from Holdover mode (dependent on the HMS pin) or when switching to another reference input, the
TIE corrector circuit measures the phase delay between the current phase (feedback signal) and the phase of the
selected reference signal. This delay value is stored in the TIE corrector circuit. This circuit creates a new virtual
reference signal that is at the same phase position as the feedback signal. By using the virtual reference, the PLL
minimizes the phase transient it experiences when it switches to another reference input or recovers from Holdover
mode.
The delay value can be reset by applying a logic low pulse to the TIE corrector circuit clear pin (TIE_CLR). A
minimum reset pulse width is 20 ns. This results in a phase alignment between the input reference signal and the
output clocks and frame pulses as shown in Figure 15 on page 29 and Figure 16 on page 31. The speed of the
phase alignment correction is limited to 61 µs/s when BW_SEL=0. Convergence is always in the direction of least
phase travel. In general the TIE correction should not be exercised when Holdover mode is entered for short time
periods. TIE_CLR can be kept low continuously. In that case the output clocks will always be aligned with the
selected input reference. This is illustrated in Figure 6.
C20: 20 MHz master clock on OSCi
Time Interval Error (TIE) Corrector Circuit
C20 Clock Accuracy
+4.6 ppm
-4.6 ppm
0 ppm
-16.6
-15
-13.8
-12
Figure 5 - Out-of-Range Thresholds
-10
-9.2
-7.4
Zarlink Semiconductor Inc.
-4.6
C20
-4.6
-5
ZL30101
C20
0
0
13
C20
4.6
4.6
5
7.4
9.2
10
12
13.8
15
16.6
Frequency offset [ppm]
Out of Range
In Range
Out of Range
In Range
Out of Range
In Range
Data Sheet