LMX2430 National Semiconductor Corporation, LMX2430 Datasheet - Page 44

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

www.national.com
Reg
R4
2.0 Programming Description
2.7.3 IF_CPG - IF Synthesizer Charge Pump Current Gain (R3[19])
The IF_CPG bit controls the IF synthesizer’s charge pump gain. Two gain levels are available.
2.7.4 IF_CPT - IF Synthesizer Charge Pump TRI-STATE (R3[20])
The IF_CPT bit allows the charge pump to be switched between a normal operating mode and a high impedance output state.
This happens asynchronously with the change in the IF_CPT bit.
Furthermore, the IF_CPT bit operates in conjuction with the IF_PD bit to set a synchronous or an asynchronous powerdown
mode. Refer to Section 2.8.4 for more details on how to program the IF_PD bit.
2.7.5 IF_RST - IF Synthesizer Counter Reset (R3[21])
The IF_RST bit resets of the IF_A, IF_B and IF_R counters. After removing the reset, the IF_A and IF_B counters resume
counting in close alignment with the IF_R counter. The maximum error is one prescaler cycle.
2.8 R4 REGISTER
The R4 register contains the IF_A, IF_B, IF_P, and IF_PD control words. The IF_A and IF_B control words are used to setup the
programmable feedback divider. The detailed descriptions and programming information for each control word is discussed in the
following sections. R4[21] is always set to 0.
2.8.1 IF_A[3:0] - IF Synthesizer Swallow Counter (A Counter) (R4[6:3])
The IF_A control word is used to setup the IF synthesizer’s A counter. The A counter is a 4-bit swallow counter used in the
programmable feedback divider. The IF_A control word can be programmed to values ranging from 0 to 15.
IF_
PD
23
Divide Ratio
IF_
22
P
15
Control Bit
Control Bit
Control Bit
0
1
•
IF_CPG
IF_CPT
IF_RST
21
0
20
19
18
Register Location
Register Location
Register Location
17
3
0
0
1
R3[19]
R3[20]
R3[21]
•
16
15
DATA[20:0] FIELD
IF_B[13:0]
14
(Continued)
IF Charge Pump
Current Gain
IF Charge Pump
TRI-STATE
IF Counter Reset
13
Description
Description
Description
2
0
0
1
12
•
44
11
IF_A[3:0]
10
IF Charge Pump
Normal Operation
IF_A, IF_B and IF_R
Normal Operation
9
1 mA
LOW
8
0
0
0
1
0
0
1
•
7
Function
Function
Function
6
IF Charge Pump
Output in High
Impedance State
IF_A, IF_B and IF_R
Reset
IF_A[3:0]
5
4
HIGH
4 mA
1
1
1
3
0
0
1
1
•
2
1
ADDRESS
FIELD
[2:0]
1
0
0
0