A 1-nW 95-ppm/◦C 260-mV startup-less bandgap-based voltage reference

We present an ultra-low-power fractional bandgap-based voltage reference and a unique method of generating a small proportional-to-absolute-temperature (PTAT) current. The PTAT current is used to generate a BJT complementary-to-absolute-temperature (CTAT) voltage. We have achieved temperature compensation of the generated reference voltage by subtracting a sub-threshold MOS CTAT voltage from the BJT CTAT voltage. The difference between the two CTAT voltages is temperature stable from -50◦C to 85◦C with a mean variation of less than 95 ppm/◦C measured across chips, without any additional trim. The proposed technique eliminates the need for additional start-up circuitry, which is mandatory for conventional architectures. The 260-mV voltage reference designed in a 180-nm CMOS process has a measured line regulation of 0.23 %/V and consumes 1 nW at room temperature