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| LMX2581_16 Datasheet, PDF (12/56 Pages) Texas Instruments – LMX2581 Wideband Frequency Synthesizer with Integrated VCO | |||
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LMX2581
SNAS601G â AUGUST 2012 â REVISED SEPTEMBER 2014
8 Detailed Description
www.ti.com
8.1 Overview
The LMX2581 is a synthesizer, consisting of a reference input and R divider, phase detector and charge pump,
VCO and high frequency fractional (N) divider, and two programmable output buffers. The device requires
external components for the loop filter and output buffers, which are application dependent.
Based on the oscillator input frequency (fOSC), PLL R divider value (PLL_R), PLL N Divider Value (PLL_N),
Fractional Numerator (PLL_NUM), Fractional Denominator (PLL_DEN), and VCO divider value (VCO_DIV), the
output frequency of the LMX2581 (fOUT) can be determined as follows:
fOUT = fOSC x OSC_2X / PLL_R x (PLL_N + PLL_NUM / PLL_DEN) / VCO_DIV
(1)
8.2 Functional Block Diagram
Digital
Control
Multiple Core VCO
Programmable
Capacitor Array
(256 Values)
Varactor
Diode
4 Switchable VCO Cores
Vtune
RFin
RFoutA
RFoutB
OSCin
MUX
N Divider
4/5 Prescaler
MUX
Output
Divider
Compensation
MUX
2X
MUX
R
Divider
1
Charge
Pump
CPout
LD
MUXout
Serial Interface
Control
DATA
CLK
LE
CE
12
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Copyright © 2012â2014, Texas Instruments Incorporated
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