LMX2502 datasheet(16/18 Pages) NSC

Part #	LMX2502

Description	PLLatinum??Frequency Synthesizer System with Integrated VCO

PDF	18 Pages

Scroll/Zoom	100%

Manufacturer	NSC [National Semiconductor (TI)]

Direct Link	http://www.national.com

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16 / 18 page

Programming Description (Continued)

R4 REGISTER

The R4 register address bits (R3 [3:0]) are “0111”.

Register R4 is used to set the IF N counters if the default value is not desired. This register is only active if the SPI_DEF bit in

R4 REGISTER

MSB

SHIFT REGISTER BIT LOCATION

LSB

9876543210

Data Field

Address

Field

001000

IF_A

[3:0]

IF_B

[8:0]

0111

Name

Functions

IF_A [3:0]

IF A Counter

4-bit swallow counter

≤ IF_A ≤ 15

IF_B [8:0]

IF B Counter

9-bit programmable counter

≤ IF_B ≤ 511

IF Frequency Setting:

VCO = {16 x IF_B + IF_A} x fOSC / IF_R where (IF_A < IF_B)

where

VCO: Output frequency of IF voltage controlled oscillator (IF VCO)

IF_B: Preset divide ratio of binary 9-bit programmable counter (1

≤ IF_B ≤ 511)

IF_A: Preset divide ratio of binary 4-bit swallow counter (0

≤ IF_A ≤ 15)

IF_R: Preset divide ratio of binary 9-bit programmable reference counter (2

≤ IF_R ≤ 511)

OSC: Reference oscillator frequency

LMX2502 Datasheet(PDF) 16 Page - National Semiconductor (TI)