Method and apparatus for achieving accurate temperature-invariant sampling frequencies in a multiple message non-volatile multilevel analog signal recording and playback system

摘要

An apparatus and method for achieving accurate temperature-invariant sampling frequencies in a device, such as, a multiple message non-volatile multilevel analog signal recording and playback system is described. An oscillator is used to generate an oscillation frequency. A bandgap voltage generator generates a zero temperature coefficient voltage reference (V(OTC)) that is independent of temperature. This V(OTC) is applied to the oscillator. A variable temperature coefficient voltage (V(TC)) that compensates for temperature coefficient variations of a resistor to which V(TC) is applied produces a stable oscillator current Iosc. Therefore, the stable oscillator current Iosc is likewise independent of the temperature coefficient variations of the resistor. The stable oscillator current Iosc is applied to the oscillator such that the oscillator generates a stable temperature-invariant oscillation frequency. A digital divider is used to digitally divide the stable oscillation frequency by a predetermined amount to produce an accurate temperature-invariant sampling frequency. A filter is then used to filter incoming signals utilizing a filter cutoff that tracks the sampling frequency.