fs6131 AMI Semiconductor, Inc., fs6131 Datasheet - Page 4

• 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
To understand the operation, refer to Figure 3. The M-counter (with a modulus of M) is cascaded with the dual-modulus pre-scaler. If
the prescaler modulus were fixed at N, the overall modulus of the feedback divider chain would be MXN. However, the A-counter
causes the pre-scaler modulus to be altered to N+1 for the first A outputs of the pre-scaler. The A-counter then causes the dual-
modulus prescaler to revert to a modulus of N until the M-counter reaches its terminal state and resets the entire divider. The overall
modulus can be expressed as
where M ≥ A, which simplifies to
4.1.3 Feedback Divider Programming
The requirement that M ≥ A means that the feedback divider can only be programmed for certain values below a divider modulus of 56.
The selection of divider values is listed in Table 2.
If the desired feedback divider is less than 56, find the divider value in the table. Follow the column up to find the A-counter program
value. Follow the row to the left to find the M-counter value.
Above a modulus of 56, the feedback divider can be programmed to any value up to 16383. See both Table 3 and Table 8 for additional
programming information.
Table 2: Feedback Modulus Below 56
4.1.4 Post Divider
The post divider consists of three individually programmable dividers, as shown in Figure 4.
The moduli of the individual dividers are denoted as N
AMI Semiconductor
www.amis.com
FBKDIV[13:3]
00000000001
00000000010
00000000011
00000000100
00000000101
00000000110
00000000111
M-Counter:
Specifications subject to change without notice
– Rev. 3.0, Jan. 08
f
GBL
000
16
24
32
40
48
56
8
POST1[1:0]
Divider 1
(N
Post
001
17
25
33
41
49
57
9
P1
)
P1
N
, N
A
Px
(
POST DIVIDER (N
Figure 4: Post Divider
P2
N
=
, and N
+
M
010
POST2[1:0]
Divider 2
18
26
34
42
50
58
N
) 1
-
(N
4
Post
P
×
1
+
N
P2
×
P3
N
)
N
, and together they make up the array modulus N
+
(
Feedback Divider Modulus
P
M
A
A-counter: FBKDIV[2:0]
2
Px
×
−
011
)
27
35
43
51
59
N
-
-
A
P
POST3[1:0]
Divider 3
)
3
(N
Post
P3
)
100
44
36
52
60
-
-
-
f
out
101
45
53
61
-
-
-
-
110
54
62
-
-
-
-
-
Px
.
Data Sheet
111
63
-
-
-
-
-
-