A 0.5-V Supply, 36 nW Bandgap Reference With 42 ppm/°C Average Temperature Coefficient Within −40 °C to 120 °C
U Chi-Wa, Wen‐Liang Zeng, Man‐Kay Law, Chi‐Seng Lam, Rui P. Martins
Abstract
This paper presents a switched capacitor network (SCN)-based bandgap voltage reference (BGR) circuit designed and implemented in a 65nm standard CMOS process with a wide temperature range, high precision, low supply voltage and low power consumption for IoT device application. The proposed BGR employs a 2x charge pump with ripple optimization design to supply the VEB generator, which can relax VDD from 0.9V to 0.5V. A proportional to absolute temperature (PTAT) current source is proposed to bias the PNP BJT in order to reduce the nonlinearity of VEB. Moreover, a voltage divider SCN with low leakage consideration to form the complementary to absolute temperature (CTAT) voltage is designed to reduce the nonlinearity of its coefficient, while a series-parallel SCN with adjusted clock swing to form the PTAT voltage is designed to improve the line regulation of the BGR. The measurement result shows that the proposed BGR has a temperature coefficient (TC) of 42 ppm/°C at 0.5V supply within - 40 °C to 120 °C. The line regulation is 3.2mV/V or 0.64%/V from 0.5V to 1V. Based on 6-chip test result, it shows a 3σ /μ variation of 3.08% before trimming, while 0.36% after trimming.