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National LMX2305 Data Sheet/Manual

Summary

This high-performance, low-power frequency synthesizer generates stable local oscillator signals up to 550 MHz using advanced BiCMOS technology. Perfect for critical RF communications, this component drives various portable wireless systems including cellular networks, WLANs, and pagers. The associated documentation provides comprehensive technical details, pin descriptions, operating parameters (2.65V–5.5V), and application guides necessary for system integration by electronics engineers.

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查询LMX2305供应商

PRELIMINARY August

tin re th iz

fo rs ic tio LMX2305 PLLatinum TM MHz Frequency Synthesizer for RF Personal Communications General Description Features

The LMX2305 is high performance frequency synthesizer RF operation up to MHz

with an integrated prescaler designed for RF operation up to 2.65V to 5.5V operation MHz. It is fabricated using National’s ABi C IV Bi CMOS Low current consumption: process. ICC 4.0 m A (typ) at VCC 2.75V The LMX2305 contains dual modulus prescaler which can Dual modulus prescaler: 64/65 or 128/129 select either 64/65 or 128/129 divide ratio at input fre- Internal balanced, low leakage charge pump quencies of up to MHz. LMX2305, which employs the

Small-outline, plastic, surface mount TSSOP,

digital phase lock loop technique, combined with high

0.173× wide package

quality reference oscillator and loop filter, provides the tuning voltage for the voltage controlled oscillator to gener-

Applications

ate very stable, low noise local oscillator signal.

Analog Cellular telephone systems

Serial data is transferred into the LMX2305 via three line

(AMPS, ETACS, NMT)

MICROWIRETM interface (Data, Enable, Clock). Supply volt-

Portable wireless communications

age can range from 2.65V to 5.5V. The LMX2305 features

(PCS/PCN, cordless)

very low current consumption, typically 4.0 m A at 2.75V.

Wireless local area networks (WLANs)

The LMX2305 is available in TSSOP 20-pin surface mount

Other wireless communication systems

plastic package.

Pagers

Block Diagram

TL/W/12459–1

TRI-STATEÉ is registered trademark of National Semiconductor Corporation. MICROWIRETM and PLLatinum TM are trademarks of National Semiconductor Corporation.

C1996 National Semiconductor Corporation TL/W/12459 RRD-B30M126/Printed in U. S. A. http://www.national.com

Page Summary Contents For National LMX2305 Data Sheet/Manual

Page 1 查询LMX2305供应商 PRELIMINARY August tin re th iz fo rs ic tio LMX2305 PLLatinum TM MHz Frequency Synthesizer for RF Personal Communications General Description Features The LMX2305 is high performance fre...
Page 2 Connection Diagram LMX2305 TL/W/12459–2 20-Lead (0.173× Wide) Thin Shrink Small Outline Package (TM) Order Number LMX2305TM or LMX2305TMX See NS Package Number MTC20 Pin Descriptions Pin No. Pin Name ...
Page 3 Functional Block Diagram TL/W/12459–3 Note 1: The power down function is gated by the charge pump to prevent any unwanted frequency jumps. Once the power down pin is brought low the part will go into ...
Page 4 Absolute Maximum Ratings (Notes and 2) Recommended Operating If Military/Aerospace specified devices are required, Conditions please contact the National Semiconductor Sales Power Supply Voltage Offic...
Page 5 Electrical Characteristics VCC 2.75V, VP 2.75V; b40§C TA 85§C, except as specified (Continued) Symbol Parameter Conditions Min Typ Max Units IDo-source Charge Pump Output Current VDo VP/2 b2.5 b1.0 m ...
Page 6 Functional Description The simplified block diagram below shows the 19-bit data register, the 14-bit Counter and the R15 Latch, and the 18-bit Counter (intermediate latches are not shown). The data st...
Page 7 Functional Description (Continued) PROGRAMMABLE DIVIDER (N COUNTER) The counter consists of the 7-bit swallow counter (A counter) and the 11-bit programmable counter (B counter). If the Control Bit (l...
Page 8 Functional Description (Continued) SERIAL DATA INPUT TIMING TL/W/12459–16 Notes: Parenthesis data indicates programmable reference divider data. Data shifted into register on clock rising edge. Data i...
Page 9 Analog Switch The analog switch is useful for radio systems that utilize frequency scanning mode and narrow band mode. The purpose of the analog switch is to decrease the loop filter time constant, al...
Page 10 Typical Application Example Operational Notes: TL/W/12459–22 VCO is assumed AC coupled. RIN increases impedance so that VCO output power is provided to the load rather than the PLL. Typical values are...
Page 11 Application Information LOOP FILTER DESIGN block diagram of the basic phase locked loop is shown. TL/W/12459–24 FIGURE 1. Basic Charge Pump Phase Locked Loop An example of passive loop filter configur...
Page 12 Application Information (Continued) Therefore, if we specify the loop bandwidth, 0p, and the In choosing the loop filter components trade off must be phase margin, wp, Equations through allow us to ca...
Page 13 Application Information (Continued) EXTERNAL CHARGE PUMP EXAMPLE The LMX PLLatinum series of frequency synthesizers are Typical Device Parameters bn e100, bp equipped with an internal balanced charge ...
Page 14 ti re th iz fo rs ic ti Physical Dimensions inches (millimeters) unless otherwise noted NS Package Number MTC20 20-Lead (0.173× Wide) Thin Shrink Small Outline Package (TM) Order Number LMX2305TM For ...

Manual Details

Brand National
Pages 14
File Size 229.56 KB
Published May 29, 2026
68 views

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Frequently Asked Questions

What is the recommended power supply voltage range?

The recommended operating voltage range is 2.65V to 5.5V.

How low is the current consumption of this synthesizer?

It has a very low quiescent current consumption, typically 4.0 mA at 2.75V.

What types of systems can use the LMX2305?

Applications include cellular telephone systems (AMPS, ETACS, NMT), WLANs, and pagers.

Does the device have a power-saving mode?

Yes, power down is initiated when pin PWDN is brought low. The function is gated by the charge pump reaching a TRI-STATE condition.

Which division ratios are selectable on the dual modulus prescaler?

The synthesizer can select either a 64/65 or a 128/129 divide ratio.