mk2069-04 Integrated Device Technology, mk2069-04 Datasheet - Page 7

• Manufacturer Part Number: mk2069-04
• Description: Vcxo-based Universal Clock Translator
• Manufacturer: Integrated Device Technology

External VCXO PLL Components
In general, the loop damping factor should be 0.7 or greater
to ensure output stability. A higher damping factor will create
less peaking in the passband and will further assure output
stability with the presence of system and power supply
noise. A damping factor of 4 will ensure a passband peak
less then 0.2 dB which may be required for network clock
wander transfer compliance. A higher damping factor may
also increase output clock jitter when there is excess digital
noise in the system application, due to the reduced ability of
the PLL to respond to and therefore compensate for phase
noise ingress.
Notes on setting the value of
As another general rule, the following relationship should be
IDT™ / ICS™ VCXO-BASED UNIVERSAL CLOCK TRANSLATOR
MK2069-04
VCXO-BASED UNIVERSAL CLOCK TRANSLATOR
Refer to "Crystal Tuning Load
Capacitors" Section
C
Crystal Tuning
Capacitors
P
Where:
C
S
= Value of capacitor C
C
C
L
L
C
R
S
S
R
XTAL
SET
ISET
LFR
X1
X2
LF
S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
in loop filter in Farads
C
P
56
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40
39
38
37
36
35
34
33
32
31
30
29
7
maintained between components C
filter:
C
For higher damping factors (> 1), calculate the value of C
based on a C
of 1. This will minimize baseband peaking and loop
instability that can lead to output jitter.
C
charge pump correction pulses. A C
will result in increased output phase noise at the phase
detector frequency due to this. In extreme cases where
input jitter is high, charge pump current is high, and C
small, the VCXO input voltage can hit the supply or ground
rail resulting in non-linear loop response.
The best way to set the value of C
response software available from ICS (please refer to the
following section). C
just starts affecting the passband peak.
Loop Filter Response Software
Online tools to calculate loop filter response can be found at
www.icst.com.
P
P
establishes a second pole in the VCXO PLL loop filter.
also dampens VCXO input voltage modulation by the
C
P
=
C
----- -
20
S
S
value that would be used for a damping factor
P
should be increased in value until it
VCXO AND SYNTHESIZER
P
MK2069-04
S
is to use the filter
P
and C
value that is too low
P
in the loop
REV G 090905
P
is too
P