ZL30101QDC ZARLINK [Zarlink Semiconductor Inc], ZL30101QDC Datasheet - Page 23

• Manufacturer Part Number: ZL30101QDC
• Description: T1/E1 Stratum 3 System Synchronizer
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

6.2
The ZL30101 can use either a clock or crystal as the master timing source. Zarlink application note ZLAN-68 lists a
number of applicable oscillators and crystals that can be used with the ZL30101.
6.2.1
When selecting a clock oscillator, numerous parameters must be considered. This includes absolute frequency,
frequency change over temperature, phase noise, output rise and fall times, output levels and duty cycle.
The output clock should be connected directly (not AC coupled) to the OSCi input of the ZL30101, and the OSCo
output should be left open as shown in Figure 12.
6.2.2
Alternatively, a crystal oscillator may be used. A complete oscillator circuit made up of a crystal, resistor and
capacitors is shown in Figure 13. The Telcordia GR1244-CORE Stratum 3 requirements for holdover stability and
freerun accuracy may not be met with this crystal oscillator circuit.
The accuracy of a crystal oscillator depends on the crystal tolerance as well as the load capacitance tolerance.
Typically, for a 20 MHz crystal specified with a 32 pF load capacitance, each 1 pF change in load capacitance
contributes approximately 9 ppm to the frequency deviation. Consequently, capacitor tolerances and stray
capacitances have a major effect on the accuracy of the oscillator frequency.
The crystal should be a fundamental mode type - not an overtone. The fundamental mode crystal permits a simpler
oscillator circuit with no additional filter components and is less likely to generate spurious responses. A typical
crystal oscillator specification and circuit is shown in Table 6 and Figure 13 respectively.
Master Clock
Clock Oscillator
Crystal Oscillator
1
2
3
4
Table 5 - Typical Clock Oscillator Specification
Frequency
Tolerance
Rise & fall time
Duty cycle
ZL30101
Figure 12 - Clock Oscillator Circuit
Zarlink Semiconductor Inc.
OSCo
OSCi
No Connection
ZL30101
23
20 MHz OUT
20 MHz
4.6 ppm
< 10 ns
40% to 60%
+3.3 V
+3.3 V
GND
0.1 µF
Data Sheet