2.4.3 RF_CPG - RF Synthesizer Charge Pump Current Gain (R0[19])

The RF_CPG bit controls the RF synthesizer’s charge pump gain. Two gain levels are available.

Control Bit

Register Location

Description

Function

01

RF_CPG

R0[19]

RF Charge Pump

Current Gain

LOW

1mA

HIGH

4mA

2.4.4 RF_CPT - RF Synthesizer Charge Pump TRI-STATE (R0[20])

The RF_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 RF_CPT bit.

Furthermore, the RF_CPT bit operates in conjuction with the RF_PD bit to set a synchronous or an asynchronous powerdown

mode. Refer to Section 2.5.4 for more details on how to program the RF_PD bit.

Control Bit

Register Location

Description

Function

01

RF_CPT

R0[20]

RF Charge Pump

TRI-STATE

RF Charge Pump

Normal Operation

RF Charge Pump

Output in High

Impedance State

2.4.5 RF_RST - RF Synthesizer Counter Reset (R0[21])

The RF_RST bit resets the RF_A, RF_B and RF_R counters. After removing the reset, the RF_A and RF_B counters resume

counting in close alignment with the RF_R counter. The maximum error is one prescaler cycle.

Control Bit

Register Location

Description

Function

01

RF_RST

R0[21]

RF Counter Reset

RF_A, RF_B and

RF_R

Normal Operation

RF_A, RF_B and

RF_R

Reset

2.5 R1 REGISTER

The R1 register contains the RF_A, RF_B, RF_P, and RF_PD control words. The RF_A and RF_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.

Reg

23

22

21

20

19

18

17

16

15

14

13

12

11

10

9876543210

DATA[20:0] FIELD

ADDRESS

[2:0]

FIELD

R1

RF_

PD

RF_

P

LMX2430/33

RF_B[14:0]

LMX2430/33

RF_A[3:0]

001

R1

RF_

PD

RF_

P

LMX2434

RF_B[13:0]

LMX2434

RF_A[4:0]

001

2.5.1 LMX243x RF Synthesizer Swallow Counter

2.5.1.1 RF_A[3:0] - LMX2430/33 RF Synthesizer Swallow Counter (A Counter) (R1[6:3])

The RF_A control word is used to setup the RF synthesizer’s A counter. For both the LMX2430 and LMX2433, the A counter is

a 4-bit swallow counter used in the programmable feedback divider. The RF_A control word can be programmed to values ranging

from 0 to 15.

Divide Ratio

LMX2430/33

RF_A[3:0]

321

0

0

000

0

1

000

1

•

•••

•

15

111

1

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