This paper presents a novel architecture of a static self-calibrating programmable voltage reference with nanoampere current consumption. The output voltage is generated by a programmable impedance matrix, based on MOS transistors and resistors, and periodically calibrated with a duty-cycled bandgap. In application domains where the temperature exhibits a low rate-of-change, an average current consumption of 6.5 nA is achieved, largely outperforming all the previously reported switched-capacitor or floating-gate architectures. Implemented in 55-nm CMOS technology, the reference exhibits a 0.4-to-2.5-V output voltage range, over the -20 to +80°C temperature range.