A low cost microcontroller compensated crystal oscillator

A Microcontroller Compensated Crystal Oscillator (MCXO) is described which employs varactor compensation using a high precision digital to analog converter (DAC) and analog to digital converter (ADC). A proven analog Temperature Compensated Crystal Oscillator (TCXO) design was enhanced by adding a state-of-the-art microcontroller subsystem. The resulting design maintains low cost while preserving the high density packaging of the parent TCXO design. Development is on going, with a currently achievable temperature stability of plus or minus 0.5 ppm from minus 40 to plus 85 degrees C using an AT cut crystal. MCXO's are calibrated after all packaging is completed, thus reducing manufacturing costs. Recalibration, to compensate for effects such as aging, can be performed at any time through one of the four device pins. The complete MCXO is assembled in a 1/spl times/1 inch footprint package. Typical power consumption is 125 milliwatts from a single 5 volt supply.