A 2.5-nA Area-Efficient Temperature-Independent 176-/82-ppm/{\deg}C CMOS-Only Current Reference in 0.11-$\mu$m Bulk and 22-nm FD-SOI

TL;DR

This paper presents a highly area-efficient, temperature-independent current reference operating at nanoampere levels, suitable for IoT sensors, fabricated in 0.11-μm bulk and 22-nm FD-SOI technologies, with minimal silicon area and robust PVT stability.

Contribution

It introduces a novel nA-range constant-with-temperature current reference using a self-cascode MOSFET biased by a low-power voltage reference, with a TC calibration mechanism, demonstrated in two advanced CMOS technologies.

Findings

Achieves 2.3-2.5 nA current with low line sensitivity

Consumes around 16 nW power in both technologies

Uses minimal silicon area (0.0106 mm² in 0.11 μm, 0.0026 mm² in 22 nm)

Abstract

Internet-of-Things (IoT) applications require nW-power current references that are robust to process, voltage and temperature (PVT) variations, to maintain the performance of IoT sensor nodes in a wide range of operating conditions. However, nA-range current references are rarely area-efficient due to the use of large gate-leakage transistors or resistors, which occupy a significant silicon area at this current level. In this paper, we introduce a nA-range constant-with-temperature (CWT) current reference, relying on a self-cascode MOSFET (SCM) biased by a four-transistor ultra-low-power voltage reference through a single-transistor buffer. The proposed reference includes a temperature coefficient (TC) calibration mechanism to maintain performance across process corners. In addition, as the proposed design relies on the body effect, it has been fabricated and measured in 0.11-$\mu$m bulk and 22-nm fully-depleted silicon-on-insulator (FD-SOI) to demonstrate feasibility in both technology types. On the one hand, the 0.11-$\mu$m design consumes a power of 16.8 nW at 1.2 V and achieves a 2.3-nA current with a line sensitivity (LS) of 2.23 %/V at 25{\deg}C and a TC of 176 ppm/{\deg}C at 1.2 V from -40 to 85{\deg}C. On the other hand, the 22-nm design consumes a power of 16.3 nW at 1.5 V and achieves a 2.5-nA current with a 1.53-%/V LS at 25{\deg}C and an 82-ppm/{\deg}C TC at 1.5 V from -40 to 85{\deg}C. Thanks to their simple architecture, the proposed references achieve a silicon area of 0.0106 mm$^2$ in 0.11 $\mu$m and 0.0026 mm$^2$ in 22 nm without compromising other figures of merit, and are thus competitive with state-of-the-art CWT references operating in the same current range.