Design of a fixed number stage programmable differential ring oscillator

Abstract

Aiming at the problem that the frequency and phase adjustment of ring oscillator requires changing the number of inverter stages and analog switch's selection position, a fixed number stages programmable differential ring oscillator is proposed. By adding an exclusive-OR gate to the input of the traditional differential delay unit, a new differential delay unit is designed. The new differential delay unit can be programmed to perform inverter unit or fixed delay unit functions. Through the derivation of the truth table of the new differential delay unit, when the input logic level of the exclusive-OR gate is low, the new differential delay unit performs the inverter unit function. When the input logic level of the exclusive-OR gate is high, the new differential delay unit performs the fixed delay unit function. Using a fixed number stages, multiple stages in series, and closed-loop feedback connection, a fixed number stages programmable differential ring oscillator is designed. By programming the number of high and low logic levels at the input of the exclusive-OR gate, the number of inverter units and fixed delay units of the programmable differential ring oscillator is controlled. So the programmable differential ring oscillator can achieve the frequency and phase adjustment. Taking a four stages programmable ring oscillator as an example, the principle of how to achieve frequency adjustment and phase adjustment of is introduced. In the multisim software, the circuit simulation of the four stages programmable differential ring oscillator is performed, achieving and phase adjustment. Frequency adjustment include 1, 2, and 4 divisions. It is verified that the fixed number stages programmable ring oscillator can achieve frequency adjustment and phase adjustment without reconfiguring the circuit.