Title :
A 2-MHZ, process and voltage compensated clock oscillator for biomedical implantable SoC in 0.18-μm CMOS
Author :
Bhamra, Hansraj ; Irazoqui, Pedro
Author_Institution :
Center for Implantable Devices, Purdue Univ., West Lafayette, IN, USA
Abstract :
We present the design and performance of a power and area efficient, process and voltage compensated, 2-MHz clock oscillator for state-of-the art wireless biomedical implantable systems-on-chip. The design presented in this paper is based on a fully differential three-stage ring oscillator with replica feedback bias, a novel process detection circuit, and a novel differential comparator to save power and area. The design of the comparator ensures the rail-to-rail swing and further improves power-supply-rejection-ratio (PSRR). The process corner sensing scheme is based on the leakage current of the device which generates control voltage for the replica feedback bias circuit. A total of 66 chip samples were collected from various locations on multiple full wafers and average variation of ±2.81% with process corner was measured at room temperature. The variation in clock frequency with supply was 0.11% for the voltage range of 1.9V-3V. The design of oscillator is intended for the RF powering scheme and it occupies 0.018 μm2 in 0.18-μm CMOS. The clock oscillator consumes 12μW from a 1.8 V regulated supply.
Keywords :
CMOS analogue integrated circuits; comparators (circuits); compensation; detector circuits; electric sensing devices; feedback oscillators; integrated circuit design; leakage currents; prosthetic power supplies; radiofrequency integrated circuits; radiofrequency oscillators; system-on-chip; voltage control; wireless sensor networks; CMOS; PSRR; RF powering scheme; SoC; clock oscillator; control voltage generation; differential comparator; frequency 2 MHz; fully differential three-stage ring oscillator; leakage current; multiple full wafer; power 12 muW; power-supply-rejection-ratio; process corner sensing scheme; process detection circuit; process-voltage compensation; rail-to-rail swing; replica feedback bias circuit; size 0.18 mum; temperature 293 K to 298 K; voltage 1.8 V; voltage 1.9 V to 3 V; wireless biomedical implantable systems-on-chip; Clocks; Frequency measurement; Ring oscillators; System-on-chip; Temperature measurement; Voltage control;
Conference_Titel :
Circuits and Systems (ISCAS), 2013 IEEE International Symposium on
Conference_Location :
Beijing
Print_ISBN :
978-1-4673-5760-9
DOI :
10.1109/ISCAS.2013.6571918