fs6131 AMI Semiconductor, Inc., fs6131 Datasheet - Page 7

• Manufacturer Part Number: fs6131
• Description: Fs6131-01g Programmable Line Lock Clock Generator Ic
• Manufacturer: AMI Semiconductor, Inc.

FS6131-01/FS6131-01g Programmable Line Lock Clock Generator IC
4.3 Loop Gain Analysis
For applications where an external loop filter is required, the following analysis example can be used to determine loop gain and
stability.
The loop gain of a PLL is the product of all of the gains within the loop.
The transfer function of the phase detector and charge pump combination is (in A/rad):
The transfer function of the loop filter is (in V/A):
The VCO transfer function (in rad/s, and accounting for the phase integration that occurs in the VCO) is:
The transfer function of the feedback divider is:
Finally, the sampling effect that occurs in the phase detector is accounted for by:
The loop gain of the PLL is:
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Specifications subject to change without notice
– Rev. 3.0, Jan. 08
K
LOOP
K
(
K
LF
s
)
SAMP
(
=
s
)
K
K
=
(
VCO
s
PD
K
)
sC
K
=
PD
K
(
2
s
LF
⎛
⎜
⎜
⎜
⎝
F
)
7
+
1
=
(
=
=
−
⎛
⎜
⎜
⎜
⎜
⎝
s
I
)
2
R
e
chgpump
N
K
π
2
1
⎛ −
LF
π
⎜
⎝
s
A
F
VCO
1
s
VCO
+
f
REF
(
⎛
⎜
⎝
1
s
1
⎞
⎟
⎠
s
)
1
K
⎞
⎟
⎟
⎟
⎠
sC
f
F
REF
K
1
⎞
⎟
⎠
SAMP
⎞
⎟
⎟
⎟
⎟
⎠
(
s
)
Data Sheet