0.45-V 5.4-nW switched-capacitor bandgap reference with intermittent operation and improved supply immunity

Abstract

Switched-capacitor networks have been used as bandgap references (BGRs) to replace the area-consuming resistors in ultra-low power applications, incorporated with voltage doubler (2X) charge pumps to operate at low supply voltages. However, the open-loop charge pumps are sensitive to supply and load variations. Therefore, in this work, constant bias currents are added to the cross-coupled 2X charge pumps to reduce the supply sensitivity, and also to reduce the output ripples without using large capacitors. To further reduce the power consumption, a low-leakage sample and hold (S&H) circuit is used for an intermittent operation, the active/idle duty ratio of the BGR core is 1/15. Designed in standard 65 nm CMOS, the proposed BGR reaches a temperature coefficient of 64 ppm/°C consuming only 5.4 nW with a minimum supply of 0.45 V (simulated).