AN2638 Freescale Semiconductor / Motorola, AN2638 Datasheet - Page 2

• Manufacturer Part Number: AN2638
• Description: Effects of Clock Jitter on the MPC8260 (HiP3 and HiP4)
• Manufacturer: Freescale Semiconductor / Motorola

Clock Jitter
Clock Jitter
1 Clock Jitter
Clock jitter is defined as when the clock’s output varies—either leads or lags—from its ideal position. Clock
jitter can be classified as one of the three following categories:
1.1 Cycle to Cycle Jitter
In an ideal case all clock waveforms should have equal periods. i.e. t
However, a cycle to cycle jitter is the difference between every two consecutive periods of a periodic
waveform. Figure 1 represents the following relationships:
1.2 Time Interval Jitter
Time interval jitter can be differentiated between long term and short term clock jitter. The long-term jitter
measurement is the maximum change in the clock output transition from ideal clock position over many
clock cycles.Figure 2 represents the long term clock jitter measurement.
2
Clock Jitter
Ideal Clock
•
•
•
Cycle to cycle jitter
Time interval jitter
Period jitter
T
T
Total jitter = T
j1=
j2=
t
t
y -
x -
t
Effects of Clock Jitter on the MPC8260 (HiP3 and HiP4)
t
z
y
Freescale Semiconductor, Inc.
t
x
j1
For More Information On This Product,
+ T
j2
Figure 1. Cycle to Cycle Jitter
Figure 2. Time Interval Jitter
Go to: www.freescale.com
t
Y
x =
t
y =
t
z .....
t
z
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