IEEE JOURNAL OF SOLID-STATE CIRCUITS, v.53, no.8, pp.2311 - 2318
This paper proposes a 32.7 kHz self-biased wake-up timer using temperature-insensitive resistive current. A dual-loop structure with supply-regulation loop and frequency-locked loop determines the regulated voltages at both ends of a temperature-compensated resistor and cancels out the amplifier offset voltages, thus generating temperature-insensitive resistive current for the switched capacitor. Moreover, a self-biasing scheme in low-power design reduces the power variation across the temperature range and eliminates the necessity of a sub-μA reference current generator. The proposed timer with its start-up circuit generates <12 ms lock time, which is 20 times less than what obtained without a start-up circuit, and exhibits a long-term frequency stability of 10 ppm and a temperature coefficient of 13.2 ppm/°C with an energy efficiency of 1.08 nW/kHz.