LMX2430 National Semiconductor Corporation, LMX2430 Datasheet - Page 41

• Manufacturer Part Number: LMX2430
• Description: Pllatinum Dual High Frequency Synthesizer For Rf Personal Communications
• Manufacturer: National Semiconductor Corporation

2.0 Programming Description
2.5.1.2 RF_A[4:0] - LMX2434 RF Synthesizer Swallow Counter (A Counter) (R1[7:3])
The LMX2434 A counter is a 5-bit swallow counter used in the programmable feedback divider. The RF_A control word can be
programmed to values ranging from 0 to 31.
2.5.2 LMX243x RF Synthesizer Programmable Binary Counter
2.5.2.1 RF_B[14:0] - LMX2430/33 RF Synthesizer Programmable Binary Counter (B Counter) (R1[21:7])
The RF_B control word is used to setup the RF synthesizer’s B counter. For both the LMX2430 and LMX2433, the B counter is
a 15-bit programmable binary counter used in the programmable feedback divider. The RF_B control word can be programmed
to values ranging from 3 to 32767. Divide ratios less than 3 are prohibited.
2.5.2.2 RF_B[13:0] - LMX2434 RF Synthesizer Programmable Binary Counter (B Counter) (R1[21:8])
The LMX2434 B counter is a 14-bit programmable binary counter used in the programmable feedback divider. The RF_B control
word can be programmed to values ranging from 3 to 16383. Divide ratios less than 3 are prohibited.
2.5.3 LMX243x RF Synthesizer Prescaler Select
2.5.3.1 RF_P - LMX2430/33 RF Synthesizer Prescaler Select (R1[22])
Both the LMX2430 and LMX2433 RF synthesizers utilize a selectable dual modulus prescaler. An 8/9 or a 16/17 prescale ratio
can be selected.
2.5.3.2 RF_P - LMX2434 RF Synthesizer Prescaler Select (R1[22])
The LMX2434 RF synthesizer utilizes a selectable dual modulus prescaler. A 16/17 or a 32/33 prescale ratio can be selected.
Divide
32767
Divide
Ratio
16383
Ratio
3
4
•
3
4
•
Divide Ratio
31
0
1
•
14
0
0
1
•
13
Control Bit
Control Bit
0
0
1
•
RF_P
RF_P
13
0
0
1
•
12
0
0
1
•
12
0
0
1
•
11
0
0
1
•
Register Location
Register Location
4
0
0
1
•
11
0
0
1
•
10
R1[22]
R1[22]
0
0
1
•
10
0
0
1
•
9
0
0
1
•
9
0
0
1
•
(Continued)
3
0
0
1
•
LMX2430/33
RF Prescaler Select
LMX2434
RF Prescaler Select
8
0
0
1
•
Description
Description
8
0
0
1
•
LMX2430/33
RF_B[14:0]
RF_B[13:0]
LMX2434
7
0
0
1
41
•
7
0
0
1
•
RF_A[4:0]
LMX2434
6
0
0
1
•
2
0
0
1
•
6
0
0
1
•
8/9 Prescaler
Selected
16/17 Prescaler
Selected
5
0
0
1
•
5
0
0
1
•
0
0
4
0
0
1
•
4
0
0
1
•
Function
Function
1
0
0
1
•
3
0
0
1
•
3
0
0
1
•
16/17 Prescaler
Selected
32/33 Prescaler
Selected
2
0
1
1
•
2
0
1
1
•
1
1
1
1
0
1
•
1
1
0
1
•
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0
0
1
1
•
0
1
0
1
0
1
0
1
•
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