A body bias generator with wide supply-range down to threshold voltage for within-die variability compensation

Abstract

A body bias generator (BBG) for fine-grain body biasing (FGBB) that can operate under wide supply-range is proposed. While FGBB is effective in reducing variability and power consumption, a number of BBGs are required on a die and therefore simplified design of BBGs is necessary. This paper proposes a cell-based design of a BBG that generates forward and reverse body bias voltages only from a core supply voltage ranging from the near threshold of 500mV to the nominal voltage of 1.2V. This wide operating range is achieved by a low voltage error amplifier with a Vth biasing scheme achieved by internal switched-capacitor charge pumping. We fabricated the forward/reverse BBG in a 65nm low power CMOS process to control 0.22mm2 of core circuit with the area overhead of 2.3% for the BBG.