A 2.5-μW Beyond-the-Rails Current Sensor With a Tunable Voltage Reference and ±0.6% Gain Error From −40 ◦C to +85 ◦C

Roger Zamparette*, Kofi Makinwa

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
147 Downloads (Pure)


This letter presents a low-power, fully integrated current sensor for Coulomb-counting. It employs a hybrid delta–sigma modulator ( ΔΣM ) with an FIR-DAC to digitize the voltage drop across a shunt. The modulator’s first stage consists of a capacitively coupled chopper amplifier, which enables a beyond-the-rails (−0.3 to 5 V) input common-mode voltage range from a 1.8-V supply. A tunable voltage reference is used to accurately compensate for the large temperature coefficient ( ∼3500 ppm/°C) of low-cost metal shunts. With a 20- mΩ on-chip shunt, ±2 A currents can be digitized with 0.35% gain error from −40°C to 85°C, after a 1-point trim. With a 3- mΩ PCB trace, currents up to ±15 A can be digitized with 0.6% gain error over the same temperature range. Fabricated in a standard 0.18- μm CMOS process, the sensor occupies 1.6 mm2 and consumes 2.5 μW , which is 3× less than the state of the art. It also achieves competitive energy efficiency, with a figure of merit (FoM) of 149 dB.

Original languageEnglish
Pages (from-to)264 - 267
Number of pages4
JournalIEEE Solid-State Circuits Letters
Publication statusPublished - 2022

Bibliographical note

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  • coulombcounting
  • current sensor
  • Fully-integrated
  • high-side
  • hybrid delta-sigma modulator
  • on-chip shunt resistor
  • PCB trace shunt resistor


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