A very low power area efficient CMOS only bandgap reference

The design of a novel all-MOS low-power bandgap reference in an open loop topology is described. A forward biased p-n junction with complementary to absolute temperature coefficient (CTAT) is combined with a cascade of Self-Cascode MOSFET (SCM) structures providing a proportional to absolute temperature (PTAT) voltage to create the bandgap voltage reference. Using the Advanced Compact MOSFET (ACM) model the design of the cascade of SCMs is fairly straightforward. The design methodology is based on the concept of inversion level using current as the main variable. At room temperature, the nominal output reference voltage is 1.32V, and the total current consumption is 65nA (20nA for the current generator and 45nA for the bandgap reference itself). The circuit has been integrated in a 0.18μm standard CMOS process, and occupies an area of 0.01mm2. Power supply sensitivity is +/-0.7% from 1.55V (minimum operation voltage) to 3.3V After trimming, temperature compensation is attained with a total bandgap voltage variation of 0.6% from -40°C to 125°C, equivalent to 36ppm/°C.