摘要
MAX2754为单片、带线性调制输入的压控振荡器(VCO)，适用于2.4GHz至2.5GHz ISM频段，尤其适合直接采用频率调制发送结构的FSK调制系统。这个芯片除了标准的频率调整输入外还可以接收线性调制输入。频率调整范围从1145MHz至1250MHz (1/2 LO)，可支持输入频率高达110MHz。VCO是基于Maxim专有的单片集成VCO技术，所有的VCO单元集中在一块芯片上，包括变容二极管和电感器。
MAX2754线性调制输入提供了一种在调谐输入电压范围内以固定的调制灵敏度直接对VCO调频的方法。在保证的频率范围内，典型的频率偏差是-500kHz ，线性度为±4%。输入电压的调整范围是+0.4V至+2.4V，振荡器的频率由工厂预置，确保频率限制范围。振荡器信号经过输出放大器(内部匹配到50)缓冲，以提供高输出能力、并且使振荡器与负载阻抗变化相隔离。
MAX2754的工作电压为+2.7V至+5.5V。该芯片提供一种数控关断模式，可实现灵活的电源管理。关闭后，电源电流减小到0.2μA。工作模式下能量消耗也只有41mW。
MAX2754采用8引脚μMAX 封装，是尺寸最小、最完备的2.4GHz直接调制VCO解决方案。
Abstrac
The MAX2754 self-contained, linear modulation, voltage-controlled oscillator (VCO) is intended for use in the 2.4GHz to 2.5GHz ISM band, particularly for FSK modulation systems that utilize a direct frequency-modulation transmit architecture. This device features a linear modulation input in addition to the standard frequency tuning input. The frequency tuning range of 1145MHz to 1250MHz (1/2 LO) also supports an IF up to 110MHz with low side LO. The VCO is based on Maxim’s proprietary monolithic VCO technology, where all VCO components are integrated on-chip, including the varactor and inductor.
The MAX2754 linear modulation input offers a means to directly FM modulate the VCO with a constant modulation sensitivity over the tuning voltage input range. Typical frequency deviation is -500kHz which is linear to ±4% over the guaranteed frequency limits. The tuning input voltage range is +0.4V to +2.4V and the oscillator frequency is factory adjusted to provide guaranteed limits. The oscillator signal is buffered by an output amplifier stage (internally matched to 50Ω) to provide higher output power and isolate the oscillator from load impedance variations.
The MAX2754 operates over a +2.7V to +5.5V supply range. This device also provides a digitally controlled shutdown mode to permit implementation of sophisticated power-supply management. In shutdown, the supply current is reduced to 0.2μA. Even when active, power consumption is a modest 41mW. The MAX2754 is packaged in the miniature 8-pin μMAX to offer the world’s smallest, complete 2.4GHz directmodulation VCO solution.
