A Design of Fast-Settling, Low-Power 4.19-MHz Real-Time Clock Generator With Temperature Compensation and 15-dB Noise Reduction

Abstract

This paper presents a fast-settling, low-power, low-noise real-time clock (RTC) generator for a 4.194304-MHz crystal oscillator. The fast settling reduces the startup time of the proposed RTC generator using a negative transcondutance booster and a crystal energy booster. The low power is only operated to reduce the total power consumption in the standby mode with the use of a peak-and-low detector. To achieve the electromagnetic interference (EMI) reduction, a pseudorandom number generator is used. The temperature compensation reduces the frequency offset from 16 to 1 ppm depending on the temperature variation. The proposed RTC generator is fabricated using a 0.18- $\mu \text{m}$ CMOS and the core area is $0.4 \,\,\text {mm} \times 0.7\,\, \text {mm}$ . The power consumption is $54~\mu \text{W}$ from a 1.8-V supply voltage. The measured startup time can be reduced by 90% from 4 ms to $400~\mu \text{s}$ with the proposed 4.194304-MHz XTAL driver. The current consumption in the standby mode is reduced by up to 700 nA. The measured frequency variation is up to a 1-ppm operation under a temperature change from −40 °C to 60 °C. The measured output peak power is reduced by up to 15 dB in the EMI reduction mode.