A Low-Power and Compact Voltage Reference with Temperature Coefficient and Voltage Accuracy Calibration

A low-power and compact voltage reference (VR) featuring temperature coefficient (TC) and voltage accuracy (VA) calibration is proposed in this paper. The proposed VR utilizes a combination of a MOS-based resistor and a poly resistor to generate a temperature coefficient-flexible current source. This current is then injected into a diode-connected MOSFET serving as an active load, forming a VR with temperature compensation. Additionally, a proportional-to-absolute-temperature current, generated by a MOS-based inverse diode, is added to the active load to fine tune the output voltage of the VR, enabling a lower TC. In order to determine the optimal circuit parameters from numerous candidates and achieve the lowest TC for the proposed VR, this paper introduces a parameter optimization strategy combining coarse and fine tuning, tailored to the proposed VR, thereby expediting the design process. To calibrate the discrepancies between simulated and measured TCs, the paper proposes an off-chip TC and VA calibration circuit, incorporating auto-calibration algorithms. This calibration circuit utilizes a redundant binary-coded resistor string digital-to-analog converter to mitigate the impact of resistor mismatch on calibration accuracy. The final measurement results show that the proposed VR has an effective footprint of 0.0037 mm² and a quiescent current of 850 nA. With the aid of the calibration circuit, the average TC of the VR is reduced by approximately a factor of 5.4, and the initial voltage of the voltage reference can be arbitrarily adjusted using the VA calibration circuit.