LMX2471 National Semiconductor, LMX2471 Datasheet - Page 26

• Manufacturer Part Number: LMX2471
• Description: 3.6 GHz Delta-Sigma Fractional-N PLL with 1.7 GHz Integer-N PLL
• Manufacturer: National Semiconductor

www.national.com
REGISTER
Programming Description
2.1 R0 REGISTER
Note that this register has only one control bit. The reason for this is that it enables the N counter value to be changed with a
single write statement to the PLL.
2.1.1 RF_FN[11:0] -- Fractional Numerator for RF PLL
Refer to section 2.8.1 for a more detailed description of this control word.
2.1.2 RF_N[10:0] -- RF N Counter Value
The RF N counter contains a 16/17/20/21 prescaler. Because there is only one selection of prescaler, the value that is
programmed is simply the N counter value converted into binary form. However, because this counter does have a prescaler,
there are limitations on the divider values.
R0
2040-2043
2044-2045
>
RF_N
65-66
67-70
2039
≤64
2045
71
72
...
23
22
0
0
1
.
21
20
DATA[19:0] ( Except for the RF_N Register, which is [22:0] )
0
0
1
.
19
RF_N[10:0]
18
0
0
1
.
Possible with a second or third order delta-sigma engine.
Possible with a second or third order delta-sigma engine.
17
Possible only with a second order delta-sigma engine.
Possible only with a second order delta-sigma engine
(Continued)
N values less than or equal to 64 are prohibited.
RF_C
16
0
0
1
.
N values above 2045 are prohibited.
15
14
1
1
1
.
26
13
RF_N[10:0]
0
0
1
.
12
11
0
0
1
.
10
9
0
1
0
8
.
RF_B
FN[11:0]
7
6
1
0
1
.
5
4
C3
3
1
0
1
.
RF_A
C2
2
C1
1
1
0
1
.
C0
0
0