zl30105 Zarlink Semiconductor, zl30105 Datasheet - Page 34

• Manufacturer Part Number: zl30105
• Description: Stratum 3 Redundant System Clock Synchronizer For T1/e1/sdh, Advanced Tca And H.110
• Manufacturer: Zarlink Semiconductor

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 21.
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 21 respectively.
Crystal Oscillator
1
2
3
4
5
6
ZL30105
Table 8 - Typical Crystal Oscillator Specification
Frequency
Tolerance
Oscillation mode
Resonance mode
Load capacitance
Maximum series resistance
The 100 Ω resistor and the 1 µH inductor may improve
stability and are optional.
Figure 21 - Crystal Oscillator Circuit
OSCi
OSCo
1 MΩ
Zarlink Semiconductor Inc.
ZL30105
100 Ω
34
20 MHz
20 MHz
as required
fundamental
parallel
as required
50 Ω
1 µH
Data Sheet
.