A low-temperature variation reference current source with digital counting auto-calibration scheme

Abstract Reliable current references with low temperature dependence are essential for mixed-signal and low-power systems, especially in harsh environments like space. This paper introduces a self-calibrating reference current source built using a standard UMC 0.18 μm CMOS process. The architecture employs a supply-independent current reference to drive a current-controlled oscillator, while a digital binary search algorithm monitors the oscillation frequency and automatically corrects deviations caused by environmental temperature variations. Fabricated with a CMOS 180 nm process, the prototype delivers a stable 25 μA reference current with a measured temperature coefficient of 206 ppm °C −1 across a broad temperature range from −40 °C to +115 °C. These results show that the proposed circuit offers a robust, low-variation, and self-healing reference current source suitable for space and other extreme conditions.