A regulation-free sub-0.5V 16/24MHz crystal oscillator for energy-harvesting BLE radios with 14.2nJ startup energy and 31.8pW steady-state power

This paper reports a regulation-free sub-0.5V crystal oscillator (XO) for Bluetooth Low-Energy (BLE) radios [1] that can be self-powered by harvesting the ambient energies, avoiding the loss and cost of the interim power converters. An ultra-low-voltage Dual-Mode g
_m
Scheme assisted by Scalable Self-reference Chirp Injection (SSCI) is proposed (Fig. 3.2.1) for the XO to surmount the operating challenges under an inconstant sub-0.5V V
_DD
(e.g. thermoelectric [2], ~80mV/K dependence) in both startup and steady states. Compatibility with different crystals (16/24MHz) is achieved, together with lower startup energy (14.2nJ) and steady-state power (31μW) than the recent art [3-5].