LMX2485 用于射频个人通信的 Δ-Σ 低功耗双路 PLL

The LMX2485 is a low power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL. The device is fabricated using National Semiconductor’s advanced process.

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 modulator order. Unlike analog compensation, the digital feedback 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

	LMX2485
Output Frequency (Min) (Mhz)	500
Output Frequency (Max) (Mhz)	3000
Aux Prescalers	8/9 or 16/17
Prescalers	8/9/12/13 or 16/17/20/21
VCC (V)	2.5 to 3.6

LMX2485 特性

Quadruple Modulus Prescalers for Lower Divide Ratios

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

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

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
On-chip crystal reference frequency doubler.
RF phase comparison frequency up to 50 MHz
2.5 to 3.6 volt operation with ICC = 5.0 mA at 3.0 V

LMX2485 器件用途

Cellular phones and base stations

CDMA, WCDMA, GSM/GPRS, TDMA, EDGE, PDC
Direct digital modulation applications
Satellite and cable TV tuners
WLAN Standards

LMX2485 工具与软件

培训内容	型号	软件/工具类型
LMX2485 Evaluation Module	LMX2485EVM	开发电路板/EVM