A 0.4μW/MHz Reference-Replication-Based RC Oscillator with Path-Delay and Comparator-Offset Cancellation Achieving 9.83ppm/°C from -40 to 125°C

RC oscillators as timers have shown improved frequency stability in recent years [1]–[23]. However, controlling their robustness against PVT variations often incurs extra area and power budgets. The closed-loop RC oscillators ([4]–[13]), aided by a frequency-locked loop (FLL), can outperform their open-loop counterparts in terms of frequency stability, but at the expense of area, power and circuit complexity (e.g. switched resistors [8]–[12] and polynomial calibration [4], [6], [7], [13]). For open-loop RC oscillators ([1]–[3], [14]–[23]), improving their free-running frequency stability is the crux. In [1], the open-loop R-RC oscillator compensates the resistor's 2nd-order temperature coefficient (TC) to enhance the frequency stability. Yet, multiple resistors with different TCs are required for accurate compensation, challenging the design complexity and required matching accuracy. The open-loop RC oscillators using the swing-boost [2], [15], sub-clock duty-cycling [3], and gate-leakage [16] techniques, exhibit ultra-low noise (~9.86ps) or better power efficiency (~0.67μW/MHz), but suffer from the temperature-sensitive path-delay together with the comparator offset penalizing the TC (>100ppm/°C).