A 55nm CMOS, 2.6 and worst case 6.8ppm/°C, 1.2V supply and -85dB PSR curvature compensated bandgap reference circuit for MEMS microphones

A high accuracy 55nm CMOS Bandgap Reference circuit (BGR) is designed for analog front-ends of digital MEMS microphones. Challenges of scaled technology and low 1.2 V supply voltage are addressed by means of a current mode structure adopting a cascode mirror. Moreover, the whole design is carried out using only high threshold I/O transistors, which are not supposed to work with such low supply. High precision with respect to process, voltage and temperature (PVT) variations is reached by integrating a higher order curvature correction circuit. Indeed, a 2.6 ppm/°C Temperature Coefficient (TC) is achieved in [-20, 80]°C temperature range, while the worst-case TC is 6.8 ppm/°C under all PVT variations and in [-40, 100]°C. Thanks to a high gain Error Amplifier (EA), high Power Supply Rejection (PSR), needed by high accuracy MEMS microphone building blocks, is -85.4 dB, -58.3dB and -30.3 dB at DC, 1 kHz and 1 MHz respectively. All this is accomplished with a total current consumption of only 4.5 μA, essential to deploy proposed bandgap reference inside low power systems.