MAC7100 View Datasheet(PDF) - Motorola => Freescale
Part Name
Description
Manufacturer
MAC7100 Datasheet PDF : 48 Pages
| |||
Freescale Semiconductor, Inc.
Electrical Characteristics
3.8.2.1 Jitter Information
The basic functionality of the PLL is shown in Figure 3. With each transition of the clock fcmp, the deviation
from the reference clock fref is measured and input voltage to the VCO is adjusted accordingly. The adjustment
is done continuously with no abrupt changes in the clock output frequency. Noise, voltage, temperature and
other factors cause slight variations in the control loop resulting in a clock jitter. This jitter affects the real
minimum and maximum clock periods as illustrated in Figure 4. It is important to note that the pre-scaler used
by timers and serial modules will eliminate the effect of PLL jitter to a large extent.
0
1
2
3
N–1
N
tMIN1
tNOM
tMAX1
tMIN(N)
tMAX(N)
Figure 4. Jitter Definitions
The relative deviation of tNOM is at its maximum for one clock period, and decreases towards zero for larger
number of clock periods (N). Thus, jitter is defined as:
J(N)
=
max
1 – -t-M----A---X----(--N-----)- ,
N ⋅ tNOM
1
–
-t--M----I-N----(---N----)--
N ⋅ tNOM
For N < 100, the following equation is a good fit for the maximum jitter:
J(N)
=
---j-1---
N
+
j2
J(N)
01
5
10
15
20
N
Figure 5. Maximum Bus Clock Jitter Approximation
16
MAC7100 Microcontroller Family Hardware Specifications
MOTOROLA
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
For More Information On This Product,
Go to: www.freescale.com
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