zl30100 Zarlink Semiconductor, zl30100 Datasheet - Page 23

• Manufacturer Part Number: zl30100
• Description: T1/e1 System Synchronizer
• Manufacturer: Zarlink Semiconductor

6.2
The ZL30100 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 ZL30100.
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 ZL30100, and the OSCo
output should be left open as shown in Figure 13.
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 14.
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.
Master Clock
Clock Oscillator
Crystal Oscillator
1
2
3
4
Table 6 - Typical Clock Oscillator Specification
Frequency
Tolerance
Rise & fall time
Duty cycle
ZL30100
Figure 13 - Clock Oscillator Circuit
OSCo
Zarlink Semiconductor Inc.
OSCi
No Connection
ZL30100
23
20 MHz OUT
< 10 ns
20 MHz
as required
40% to 60%
+3.3 V
+3.3 V
GND
0.1 µF
Data Sheet