CDCE62002 Datasheet, PDF (36/49 Pages) Texas Instruments – Four Output Clock Generator/Jitter Cleaner With Integrated Dual VCOs

CDCE62002
SCAS882A – JUNE 2009 – REVISED JULY 2009.............................................................................................................................................................. www.ti.com
Loop Filter
Figure 28 depicts the loop filter topology of the CDCE62002. It facilitates both internal and external
implementations providing optimal flexibility.
EXT_LFP
EXT_LFN
internal
external
VB
+
PFD/
CP
-
C1
internal
external
Registers 0
25 24 23 22
R3
C3
R2 ^C2
Figure 28. CDCE62002 Loop Filter Topology
Internal Loop Filter Component Configuration
Figure 28 illustrates the switching between four fixed internal loop filter settings and the external loop filter
setting. Table 19 shows that the CDCE62002 has 16 settings different settings for the loop filter. Four of the
settings are internal and twelve are external.
LFRCSEL
321
0
000
0
000
1
001
0
001
1
010
0
010
1
011
0
011
1
100
0
100
1
101
0
101
1
110
0
110
1
111
0
111
1
Table 19. CDCE62002 Loop Filter Settings
Loop Filter
Internal
Internal
Internal
Internal
External
External
External
External
External
External
External
External
External
External
External
External
C1
1.5 pF
1.5 pF
1.5 pF
1.5 pF
X
X
X
X
X
X
X
X
X
X
X
X
C2
473.5 pF
473.5 pF
473.5 pF
473.5 pF
X
X
X
X
X
X
X
X
X
X
X
X
3 db Corner
R2
R3
C3
C3R3
4.0k
5k
2.5 pF
12 MHz
4.0k
5k
2.5 pF
12 MHz
2.7k
5k
2.5 pF
12 MHz
2.7k
5k
2.5 pF
12 MHz
X
20k 112 pF
70 kHz
X
20k 112 pF
70 kHz
X
20k 112 pF
70 kHz
X
20k 112 pF
70 kHz
X
10k 100 pF
150 kHz
X
10k 100 pF
150 kHz
X
10k 100 pF
150 kHz
X
10k 100 pF
150 kHz
X
5k
100 pF
300 kHz
X
5k
64 pF
500 kHz
X
5k
48 pF
700 kHz
X
5k
38 pF
800 kHz
Charge
Pump
Current
1.5 mA
400 µA
250 µA
150 µA
1.0 mA
2.0 mA
3.0 mA
3.75 mA
1.0 mA
2.0 mA
3.0 mA
3.75 mA
1.0 mA
2.0 mA
3.0 mA
3.75 mA
36
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