Datasheet > LMX2485_08

LMX2485_08

更新时间： 2024-01-27 17:12:16

品牌	Logo	应用领域
美国国家半导体 - NSC		/
页数	文件大小	规格书
40页	745K
描述
50 MHz - 3.0 GHz High Performance Delta-Sigma Low Power Dual PLLatinum⑩ Frequency Synthesizers with 800MHz Integer PLL

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LMX2485_08 数据手册

February 27, 2008

LMX2485/LMX2485E

50 MHz - 3.0 GHz High Performance Delta-Sigma Low

Power Dual PLLatinum™ Frequency Synthesizers with 800

MHz Integer PLL

Satellite and cable TV tuners

■

General Description

WLAN Standards

The LMX2485 is a low power, high performance delta-sigma

fractional-N PLL with an auxiliary integer-N PLL. The device

Features

is fabricated using National Semiconductor’s advanced pro-

cess.

Quadruple Modulus Prescalers for Lower Divide Ratios

With delta-sigma architecture, fractional spurs at lower offset

frequencies are pushed to higher frequencies outside the loop

RF PLL: 8/9/12/13 or 16/17/20/21

■

IF PLL: 8/9 or 16/17

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 LMX2485 is highly resistant to

changes in temperature and variations in wafer processing.

The LMX2485 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

Serial data for programming the LMX2485 is transferred via

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

LMX2485 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 LMX2485 is available in a 24 lead

4.0 X 4.0 X 0.8 mm LLP package.

Single word write to change frequencies with Fastlock

Wide Operating Range

LMX2485 RF PLL: 500 MHz to 3.0 GHz

■

LMX2485E RF PLL: 50 MHz to 3.0 GHz

Useful Features

Digital lock detect output

■

Hardware and software power-down control

Applications

On-chip crystal reference frequency doubler.

Cellular phones and base stations

CDMA, WCDMA, GSM/GPRS, TDMA, EDGE, PDC

■

RF phase comparison frequency up to 50 MHz

2.5 to 3.6 volt operation with I_CC= 5.0 mA at 3.0 V

■

Direct digital modulation applications

■

Functional Block Diagram

20087701

PLLatinum™ is a trademark of National Semiconductor Corporation.

200877

www.national.com

12 3 4 5 6 7...40

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与LMX2485_08相关器件

型号	品牌	获取价格	描述	数据表
LMX2485E	NSC	获取价格	50 MHz - 3.0 GHz High Performance Delta-Sigma
LMX2485E	TI	获取价格	用于射频个人通信的 50MHz 至 3GHz Δ-Σ 低功耗双路 PLL
LMX2485ESQ	NSC	获取价格	50 MHz - 3.0 GHz High Performance Delta-Sigma
LMX2485ESQ/NOPB	NSC	获取价格	IC PLL FREQUENCY SYNTHESIZER, 3000 MHz, PQCC24, 4 X 4 MM, 0.8 MM, PLASTIC, LLP-24, PLL or
LMX2485ESQ/NOPB	TI	获取价格	用于射频个人通信的 50MHz 至 3GHz Δ-Σ 低功耗双路 PLL \| RTW \|
LMX2485ESQX	NSC	获取价格	50 MHz - 3.0 GHz High Performance Delta-Sigma
LMX2485ESQX/NOPB	TI	获取价格	用于射频个人通信的 50MHz 至 3GHz Δ-Σ 低功耗双路 PLL \| RTW \|
LMX2485Q-Q1	TI	获取价格	500MHz 至 3GHz 汽车类 Δ-Σ 低功耗双路 PLL
LMX2485QSQ/NOPB	TI	获取价格	500MHz 至 3GHz 汽车类 Δ-Σ 低功耗双路 PLL \| RTW \| 24 \|
LMX2485QSQX/NOPB	TI	获取价格	500MHz 至 3GHz 汽车类 Δ-Σ 低功耗双路 PLL \| RTW \| 24 \|

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