A 32-kHz Real-Time Clock Oscillator with On-Chip PVT Variation Compensation Circuit for Ultra-Low Power MCUs

Tetsuya HIROSE
Nobutaka KUROKI
Masahiro NUMA

IEICE TRANSACTIONS on Electronics   Vol.E98-C    No.5    pp.446-453
Publication Date: 2015/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E98.C.446
Type of Manuscript: PAPER
Category: Integrated Electronics
ROSC,  RTC,  oscillator,  comparator,  PVT variation,  low-power,  

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This paper proposes an ultra-low power fully on-chip CMOS relaxation oscillator (ROSC) for a real-time clock application. The proposed ROSC employs a compensation circuit of a comparator's non-idealities caused by offset voltage and delay time. The ROSC can generate a stable, and 32-kHz oscillation clock frequency without increasing power dissipation by using a low reference voltage and employing a novel compensation architecture for comparators. Measurement results in a 0.18-μm CMOS process demonstrated that the circuit can generate a stable clock frequency of 32.55 kHz with low power dissipation of 472 nW at 1.8-V power supply. Measured line regulation and temperature coefficient were 1.1%/V and 120 ppm/°C, respectively.