Switched-Capacitor Network BasedBandgap Voltage Reference with Leakage Current Injection Techniquefor Curvature Compensation

Abstract

In a variety of electronic circuit and systems including power management unit (PMU) and analog-to-digital converter (ADC), bandgap voltage reference (BGR) is an important building block as it provides an accurate constant reference voltage that is independent to the process, supply voltage and temperature (PVT) variation. In the application of IoT devices, the development trend and research target is to reduce the power consumption and minimum supply voltage for BGR, while a fair temperature coefficient (TC) and line regulation performance can still be available. This project presents a switched-capacitor network (SCN) based bandgap voltage reference with leakage current injection technique for curvature compensation. The proposed BGR utilizes a deep N-well NMOS transistor to provide a high-order leakage current, which is injected into the SCN in the holding state and provides a compensation voltage for the BGR. The proposed compensation technique is energy efficient, and it does not contribute significant extra power to the whole BGR. The proposed BGR was fabricated in a 65nm CMOS process, occupying an active area of 0.0442 mm2. The measurement results show that the reference voltage is 432.4 mV under 0.5 V supply at room temperature. The average TC is 22.5ppm/°C over a temperature range of -40°C and 120°C, which is significantly improved when comparing with the previous BGRs, while the other performance indexes are still comparable with them, which validate the effectiveness of the proposed leakage current injection technique for curvature correction.