Design of a PTAT and Bandgap Current Reference with On-chip Digital Calibration

This paper presents the implementation of a bandgap current and proportional to absolute temperature (PTAT) current reference circuits. An on-chip digital calibration circuit is incorporated into the circuits to compensate for the effect of process-induced variations. A start-up circuit that functions without any external signal is also included in the bandgap. The circuits were designed and fabricated in 180 nm CMOS process. The circuits operate with a supply voltage of 1.8V and occupy a total area of 312 × 210 µm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>. The combined power consumption of the bandgap and PTAT circuits is 210 µW. Measurements in the fabricated test chip show that the bandgap circuit generates a current of 19.2 µA at ambient temperature and exhibits a temperature coefficient of 110 ppm/°C over a temperature range of 0 to 100 °C. The PTAT circuit was observed to generate a current of 3.6 µA at ambient temperature with a slope of 0.014 µA/°C over a temperature range of 0 to 100 °C.