A 1.53 mm³ crystal-less standards-compliant Bluetooth Low Energy module for volume constrained wireless sensors

Highly miniaturized wireless sensors will enable new healthcare sensing modalities such as ultra-small wearables, implantables, smart pills, etc. Bluetooth Low Energy (BLE) links to sensors improves user experience but necessitate a highly integrated, miniaturized BLE transmitter. Commercially available BLE transmitters are often unsuitable as they need a quartz crystal and multiple bulky external components, and are unable to operate from small silver oxide batteries which can have source impedances >40 Ω. While crystal-free transmitters have been published [1], they are either not standards compliant or remain research prototypes. In this paper, we present an FBAR-based (thin-Film Bulk Acoustic wave Resonator) [2] standards compliant BLE broadcaster module with an operating temperature range of 15C to +70C suitable for mass-produced volume-constrained sensors. All necessary electronics including the 65nm CMOS chip and FBAR frequency reference are integrated in a module with a volume of 1.53 mm ³ (lowest reported to date).