In various embodiments, the invention provides a clock generator and/or a
timing and frequency reference, with multiple operating modes, such power
conservation, clock, reference, and pulsed modes. The various apparatus
embodiments include a resonator adapted to provide a first signal having
a resonant frequency; an amplifier; a temperature compensator adapted to
modify the resonant frequency in response to temperature; and a process
variation compensator adapted to modify the resonant frequency in
response to fabrication process variation. In addition, the various
embodiments may also include a frequency divider adapted to divide the
first signal having the resonant frequency into a plurality of second
signals having a corresponding plurality of frequencies substantially
equal to or lower than the resonant frequency; and a frequency selector
adapted to provide an output signal from the plurality of second signals.
The output signal may be provided in any of various forms, such as
differential or single-ended, and substantially square-wave or
sinusoidal.