CMOS Analog and Mixed-Signal Circuit Design

9	Peripheral Circuits

9.1      INTRODUCTION

Knowledge of the oscillator and interface circuitry is important for a complete custom analog and mixed-signal integrated circuits. The oscillator can be used in more advanced oscillatory, such as phase-locked loop. However, the phase-locked loop is normally required for a very accurate source requirement. A basic built-in oscillator is normally sufficient for standalone analog or mixed-signal integrated circuits. The control clock is basically generated from the controller or master controller integrated circuit (IC).

9.2      OSCILLATOR

9.2.1      RING OSCILLATOR

Figure 9.1 shows a current-starved ring oscillator. The oscillation frequency of a basic ring oscillator is:

$f_{osc} = \frac{1}{n.(t_{PHL}+t_P}$