Analog temperature controlled crystal oscillator

Conceptually based upon a simple crystal oscillator circuit, an Analog Temperature Controlled Crystal Oscillator or Analogue Temperature Compensated Crystal Oscillator uses analog (analogue) techniques to correct the temperature deficencies of the whole crystal oscillator circuit, its package and its environment.

Typically the correction techniques involve the physical and electrical characterisation of the motional inductance and terminal capacitance of a crystal blank, the knowledge of which is used to create a correction polynomial, or algorithm, which in turn is implemented in circuit blocks by Electronic Design Engineers. These circuit blocks are usually simulated in a mathematical modelling software tool such as SPICE, to verify that the original measured data can be corrected adequately. Once the system performance has been verified, these circuits are then implemented in a silicon die, usually in a bulk CMOS technology. Once fabricated, this die is then embedded into an oscillator module along with the crystal blank. Due to the sub 1ppm accuracy of this type of crystal oscillator specialist packaging must be used to ensure good ageing and temperature shock characteristics. Example applications are for use in low power or battery operated consumer electronic products such as GSM or CDMA mobile phones, or GPS satelite navigation systems.