Design and Analysis of a Resistive Frequency-Locked Oscillator with Long-Term Stability Using Double Chopper Stabilization

A resistive frequency-locked loop on-chip oscillator based on a double chopper stabilization technique is proposed for the improvement of frequency stability. The temperature-sensitive nonidealities, including the reference mismatch current and amplifier offset voltage, are suppressed by a double chopper stabilization technique. A prototype chip is implemented in a 180-nm CMOS process with an active area of 0.3 mm2. The measurement results show that the frequency-locked oscillator operating at 250 kHz achieves temperature stability of 27.1 ppm/°C and long-term stability of 2.73 ppm, with the power consumption of 293 nW. The mitigation of the low-frequency flicker noise results in a 16X improvement in the long-term stability of the RFLO compared to that with no chopper technique.