A High-Order-Temperature-Compensated 328kHz On Chip RC Timer Using Time-Interleaved Resistors Achieving 1.5pJ/Cycle and 5.86ppm°C

Wireless IoT nodes can be ubiquitously applied for environmental and biomedical sensing. They are typically duty-cycled to save power consumption, thus requiring ultra-low power consumption and stable frequency. At the same time, they need to occupy a small area for the miniaturization of the nodes. Consequently, monolithic RC os-cillators have gained popularity instead of bulky crystal oscillators for their low power and CMOS compatibility [1]– [7]. Conventional RC oscillators exploit resistors with complementary temperature coefficients (TC) to compensate for the resistor’s temperature drift. They normally need precise trimming with many resistors and switch arrays, but their parasitics and off-leakage limit the TC [1] [2]. A lower TC can be achieved by applying polynomial correction with a temperature sensor, but they have relatively higher energy per cycle and normally require power-hungry digital processing [3] [4]. An alternative is to use a switched resistor [5] [6], but in [5], it either is limited only to first-order TC cancellation or requires more than 3-point trimming, while [6] has a high power and area overhead due to the two PLLs used. Time-domain trimming is proposed in [7], but it requires extensive calibration and has a large frequency ripple.