ZL30106QDG Zarlink, ZL30106QDG Datasheet - Page 23

• Manufacturer Part Number: ZL30106QDG
• Description: SONET/SDH/PDH Network Interface 64-Pin TQFP
• Manufacturer: Zarlink

Specifications of ZL30106QDG

• Package: 64TQFP
• Power Supply Type: Analog
• Typical Supply Current: 68(Max) mA
• Typical Operating Supply Voltage: 1.8|3.3 V
• Minimum Operating Supply Voltage: 1.62 V
• Maximum Operating Supply Voltage: 3.63 V

4.4.2
Holdover Mode is typically used for short durations while system synchronization is temporarily disrupted.
In Holdover Mode, the ZL30106 provides timing and synchronization signals, which are not locked to an external
reference signal, but are based on storage techniques. The storage value is determined while the device is in
Normal Mode and locked to an external reference signal.
When in Normal Mode, and locked to the input reference signal, a numerical value corresponding to the ZL30106
output reference frequency is stored alternately in two memory locations every 26 ms. When the device is switched
into Holdover Mode, the value in memory from between 26 ms and 52 ms is used to set the output frequency of the
device. The frequency accuracy of Holdover Mode is 0.01 ppm.
Two factors affect the accuracy of Holdover mode. One is drift on the master clock while in Holdover mode, drift on
the master clock directly affects the Holdover mode accuracy. Note that the absolute master clock (OSCi) accuracy
does not affect Holdover accuracy, only the change in OSCi accuracy while in Holdover. For example, a
master clock may have a temperature coefficient of
ZL30106 is in Holdover mode may result in an additional offset (over the 0.01 ppm) in frequency accuracy of
±
jitter on the reference input prior to the mode switch.
4.4.3
Normal mode is typically used when a system clock source, synchronized to the network is required. In Normal
mode, the ZL30106 provides timing and frame synchronization signals, which are synchronized to one of three
reference inputs (REF0, REF1 or REF2). The input reference signal may have a nominal frequency of 2 kHz,
8 kHz, 1.544 MHz, 2.048 MHz, 8.192 MHz, 16.384 MHz or 19.44 MHz. The frequency of the reference inputs are
automatically detected by the reference monitors.
When the ZL30106 comes out of RESET while Normal mode is selected by its MODE_SEL pins then it will initially
go into Holdover mode and generate clocks with the accuracy of its freerunning local oscillator (see Figure 12). If
the ZL30106 determines that its selected reference is disrupted (see Figure 3), it will remain in Holdover until the
selected reference is no longer disrupted or the external controller selects another reference that is not disrupted. If
the ZL30106 determines that its selected reference is not disrupted (see Figure 3) then the state machine will cause
the DPLL to recover from Holdover via one of two paths depending on the logic level at the HMS pin. If HMS=0 then
the ZL30106 will transition directly to Normal mode and it will align its output signals with its selected input
reference (see Figure 10). If HMS=1 then the ZL30106 will transition to Normal mode via the TIE correction state
and the phase difference between the output signals and the selected input reference will be maintained.
When the ZL30106 is operating in Normal mode, if it determines that its selected reference is disrupted (Figure 3)
then its state machine will cause it to automatically go to Holdover mode. When the ZL30106 determines that its
selected reference is not disrupted then the state machine will cause the DPLL to recover from Holdover via one of
two paths depending on the logic level at the HMS pin (see Figure 12). If HMS=0 then the ZL30106 will transition
directly to Normal mode and it will align its output signals with its input reference (see Figure 10). If HMS=1 then the
ZL30106 will transition to Normal mode via the TIE correction state and the phase difference between the output
signals and the input reference will be maintained.
If the reference selection changes because the value of the REF_SEL1:0 pins changes or because the reference
selection state machine selected a different reference input, the ZL30106 goes into Holdover mode and returns to
Normal mode through the TIE correction state regardless of the logic value on HMS pin.
1 ppm. Which is much greater than the 0.01 ppm of the ZL30106. The other factor affecting the accuracy is large
Holdover Mode
Normal Mode
Zarlink Semiconductor Inc.
ZL30106
±
0.1 ppm per °C. So a
23
±
10 °C change in temperature, while the
Data Sheet
±
32 ppm