ZL30105QDG ZARLINK [Zarlink Semiconductor Inc], ZL30105QDG Datasheet - Page 32

• Manufacturer Part Number: ZL30105QDG
• Description: T1/E1/SDH Stratum 3 Redundant System Clock Synchonizer for AdvancedTCA and H.110
• Manufacturer: ZARLINK [Zarlink Semiconductor Inc]

5.2.1
When selecting a clock oscillator, numerous parameters must be considered. This includes absolute frequency,
frequency change over temperature, output rise and fall times, output levels, duty cycle and phase noise.
The output clock should be connected directly (not AC coupled) to the OSCi input of the ZL30105 and the OSCo
output should be left open as shown in Figure 21.
5.2.2
Alternatively, a Crystal Oscillator may be used. A complete oscillator circuit made up of a crystal, resistor and
capacitors is shown in Figure 22.
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 8 and Figure 22 respectively.
Clock Oscillator
Crystal Oscillator
1
2
3
4
5
6
1
2
3
4
Table 8 - Typical Crystal Oscillator Specification
Frequency
Tolerance
Oscillation mode
Resonance mode
Load capacitance
Maximum series resistance
Table 7 - Typical Clock Oscillator Specification
Frequency
Tolerance
Rise & fall time
Duty cycle
ZL30105
Figure 21 - Clock Oscillator Circuit
Zarlink Semiconductor Inc.
OSCo
OSCi
No Connection
ZL30105
32
20 MHz OUT
< 10 ns
20 MHz
as required
40% to 60%
+3.3 V
+3.3 V
GND
20 MHz
as required
fundamental
parallel
as required
50
Ω
0.1 µF
Data Sheet
.