LMX2581_16 Datasheet, PDF (5/56 Pages) Texas Instruments – LMX2581 Wideband Frequency Synthesizer with Integrated VCO

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PIN
NUMBER
NAME
19
VbiasVCO
20
Vtune
21
GND
22
VrefVCO
23
VbiasCOMP
24
VregVCO
25
LD
26
BUFEN
27
GND
28
VccDIG
29
OSCin
30
MUXout
31
GND
32
VccFRAC
LMX2581
SNAS601G – AUGUST 2012 – REVISED SEPTEMBER 2014
Pin Functions (continued)
TYPE
DESCRIPTION
Output
Input
GND
Output
Output
Output
Output
Input
GND
Supply
Input
Output
GND
Vcc
Bias circuitry for the VCO. Place a 2.2 µF capacitor to GND (Preferably close to Pin 18).
VCO tuning voltage input. See the functional description regarding the minimum
capacitance to put at this pin.
VCO ground.
VCO capacitance. Place a capacitor to GND (Preferably close to Pin 18). This value should
be between 5% and 10% of the capacitance at pin 24. Recommended value is 1 µF.
VCO bias voltage temperature compensation circuit. Place a minimum 10 µF capacitor to
GND (Preferably close to Pin 18). If it is possible, use more capacitance to slightly improve
VCO phase noise.
VCO regulator output. Place a minimum 10 µF capacitor to GND (Preferably close to Pin
18). If it is possible, use more capacitance to slightly improve VCO phase noise.
Multiplexed output that can perform lock detect, PLL N and R counter outputs, Readback,
and other diagnostic functions.
Enable pin for the RF output buffer. If not used, this can be overwritten in software.
Digital Ground.
Digital Supply.
Reference input clock.
Multiplexed output that can perform lock detect, PLL N and R counter outputs, Readback,
and other diagnostic functions..
Ground for the fractional circuitry.
Supply for the fractional circuitry.
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