A 114 ppm/°C-TC 0.78%-(σ/μ) Current Reference With Minimum-Current-Search Calibration

Accuracy and stability of current references (CRs) represent challenging requirements in modern analog integrated design, dictating the need for PVT-insensitive implementations. In this brief, we investigate a solution relying on the combination of analog CR topologies with an automatic on-chip temperature calibration, based on a minimum-current-search principle. The proposed algorithm does not require explicit temperature sensing and allows improving the temperature coefficient (TC) by a factor of 3 with respect to the analog core. The CR circuit was designed in 0.18 $\mu $ m CMOS for an output current of 469 nA. Mixed-signal simulations resulted in a TC of 114 ppm/°C (averaged across 200 Monte Carlo runs) and in a relative standard deviation of 0.78% for the reference current, which are competitive results compared with the state of the art.

I. Introduction

Design techniques for reliable on-chip reference circuits have been the object of widespread research interest during recent years, due to the demanding requirements of modern mixed-signal integrated circuits (ICs) applications. In standalone-operating devices, such as wearable/implantable electronics and Internet-of-Things (IoT) nodes, performances may largely rely on the availability of accurate and stable reference quantities, to allow biasing and controlling other IC building blocks [1]. Voltage and current references (VRs, CRs) are expected to provide such quantities, despite process-voltage-temperature (PVT) variations. Furthermore, due to energy and size constraints, low power consumption and small area occupation also represent crucial requirements.