Datasheet > LMX2487_08

LMX2487_08

更新时间： 2022-12-28 22:45:41

品牌	Logo	应用领域
美国国家半导体 - NSC		半导体
页数	文件大小	规格书
40页	730K
描述
1.0 GHz - 6.0 GHz High Performance Delta-Sigma Low Power Dual PLLatinum™ Frequency Synthesizers with 3.0 GHz Integer PLL

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LMX2487_08 数据手册

April 25, 2008

LMX2487

1.0 GHz - 6.0 GHz High Performance Delta-Sigma Low

Power Dual PLLatinum™ Frequency Synthesizers with 3.0

GHz Integer PLL

General Description

Features

The LMX2487 is a low power, high performance delta-sigma

fractional-N PLL with an auxiliary integer-N PLL. It is fabricat-

ed using National Semiconductor’s advanced process.

Quadruple Modulus Prescalers for Lower Divide Ratios

RF PLL: 16/17/20/21 or 32/33/36/37

■

IF PLL: 8/9 or 16/17

With delta-sigma architecture, fractional spurs at lower offset

frequencies are pushed to higher frequencies outside the loop

bandwidth. The ability to push close in spur and phase noise

energy to higher frequencies is a direct function of the mod-

ulator order. Unlike analog compensation, the digital feed-

back technique used in the LMX2487 is highly resistant to

changes in temperature and variations in wafer processing.

The LMX2487 delta-sigma modulator is programmable up to

fourth order, which allows the designer to select the optimum

modulator order to fit the phase noise, spur, and lock time

requirements of the system.

Advanced Delta Sigma Fractional Compensation

12 bit or 22 bit selectable fractional modulus

■

Up to 4th order programmable delta-sigma modulator

Features for Improved Lock Times and Programming

Fastlock / Cycle slip reduction

■

Integrated time-out counter

Single word write to change frequencies with Fastlock

Serial data for programming the LMX2487 is transferred via

a three line high speed (20 MHz) MICROWIRE interface. The

LMX2487 offers fine frequency resolution, low spurs, fast pro-

gramming speed, and a single word write to change the

frequency. This makes it ideal for direct digital modulation

applications, where the N counter is directly modulated with

information. The LMX2487 is available in a 24 lead

4.0 X 4.0 X 0.8 mm LLP package.

Wide Operating Range

LMX2487 RF PLL: 1.0 GHz to 6.0 GHz

■

Useful Features

Digital lock detect output

■

Hardware and software power-down control

On-chip crystal reference frequency doubler.

RF phase comparison frequency up to 50 MHz

2.5 to 3.6 volt operation with I_CC= 8.5 mA at 3.0 V

Applications

■

Cellular phones and base stations

■

Direct digital modulation applications

Satellite and cable TV tuners

WLAN Standards

Functional Block Diagram

20154701

PLLatinum™ is a trademark of National Semiconductor Corporation.

201547

www.national.com

12 3 4 5 6 7...40

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