LMX2430 datasheet(40/49 Pages) NSC

40 / 49 page

2.0 Programming Description (Continued)

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

Description

Function

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

Description

Function

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

Description

Function

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

9876543210

DATA[20:0] FIELD

ADDRESS

[2:0]

FIELD

RF_

LMX2430/33

RF_B[14:0]

LMX2430/33

RF_A[3:0]

001

RF_

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

000

•

•••

•

111

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