The present invention is directed to a multi-mode crystal oscillator system selectively configurable to minimize power consumption or noise generation. Such a system is particularly applicable to the communication system of an implantable device, e.g., the microstimulator/sensor device described in U.S. Pat. Nos. 6,164,284 and 6,185,452. In such devices, their small size limits the size of the battery contained within and thus makes it essential to minimize power consumption. Additionally, the small size and battery capacity result in a limited transmission power. Furthermore, the small size limits the antenna efficiency which makes it desirable to limit any noise generation to maximize the signal-to-noise level of the resulting receive signal. Accordingly, embodiments of the present invention alternatively supply power to the oscillator in either a first mode that minimizes power consumption or a second mode that minimizes noise generation.