Efficient Mitigation of SET Induced Harmonic Errors in Ring Oscillators

Ring oscillators are one of the essential blocks in many electronic systems. Their versatility makes them suitable for many different applications including implementations for radiation environments. But under this scenario, it has been shown that the ring oscillator produces harmonic frequencies as a result of single event transient (SET) effects. We propose a SET tolerant ring oscillator which can be designed without area overhead. To achieve this goal, we force the masking of the particle impacts by configuring the duty cycle of ring oscillators. This configuration is based on the asymmetric design of odd and even stages of the ring oscillator. The validation of our proposal has been carried out with different methods. First, we simulated the injection of SETs with double exponential current sources. Second, we manufactured and measured two different test circuits, one with a fixed asymmetry and the other with a dynamic asymmetry, using a SET emulated injection. Both methods confirmed that higher harmonics can be totally removed using our design technique.