LMX2430 National Semiconductor Corporation, LMX2430 Datasheet - Page 45

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

2.0 Programming Description
2.8.2 IF_B[13:0] - IF Synthesizer Programmable Binary Counter (B Counter) (R4[20:7])
The IF_B control word is used to setup the IF synthesizer’s B counter. The B counter is a 14-bit programmable binary counter
used in the programmable feedback divider. The IF_B control word can be programmed to values ranging from 3 to 16383. Divide
ratios less than 3 are prohibited.
2.8.3 IF_P - IF Synthesizer Prescaler Select (R4[22])
The LMX243x IF synthesizer utilizes a selectable dual modulus prescaler. An 8/9 or a 16/17 prescale ratio can be selected.
2.8.4 IF_PD - IF Synthesizer Powerdown (R4[23])
The IF_PD bit is used to switch the IF PLL between a powered up and powered down mode.
Furthermore, the IF_PD bit operates in conjuction with the IF_CPT bit to set a synchronous or an asynchronous powerdown
mode. Refer to Section 2.7.4 for more details on how to program the IF_CPT bit.
Divide
16383
Ratio
3
4
•
13
Control Bit
Control Bit
0
0
1
•
IF_PD
IF_P
12
0
0
1
•
11
0
0
1
•
Register Location
Register Location
10
R4[22]
R4[23]
0
0
1
•
9
0
0
1
•
(Continued)
IF Prescaler Select
IF Powerdown
8
0
0
1
•
Description
Description
IF_B[13:0]
7
0
0
1
45
•
6
0
0
1
•
8/9 Prescaler
Selected
IF PLL Active
5
0
0
1
•
0
0
4
0
0
1
•
Function
Function
3
0
0
1
•
16/17 Prescaler
Selected
IF PLL Powerdown
2
0
1
1
•
1
1
1
1
0
1
•
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0
1
0
1
•