Describe the operation of voltage to frequency ADC.

Ans:

A voltage-to-frequency converter i.e. VFC is an oscillator that frequency is linearly proportional to a control voltage. The voltage-to-frequency converter A to D Convertor is monotonic and free of missing codes, integrates noise and can consume extremely little power.

The current-steering multivibrator voltage-to-frequency converter is in fact a current to-frequency converter quite than a VFC, but, as demonstrated in Figure below, practical circuits invariably have a voltage to-current converter at the input.

The principle of operation is evident: the current discharges the capacitor till a threshold is reached, and while the capacitor terminals are reversed, the half cycle repeats by itself. The waveform across the capacitor is a linear triangular wave, although the waveform on either terminal regarding ground is the more complicated waveform shown.

Truth Table